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268 Cards in this Set
- Front
- Back
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Define species.
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Group of physically similar organisms that can interbreed in nature.
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Define taxonomy.
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Put species into groups.
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What is the hierarchy of the Linnean system of taxonomy?
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Domain - Kingdom - Phylum - Class - Order - Family - Genus - Species
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What is the alternative theory to Spontaneous Generation?
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Evolution
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Who disproved spontaneous generation? When? How?
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Redi. 1668. Via maggots (on meat).
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Define evolution.
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New species coming from old species.
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When were the first cells discovered?
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1600s by Van Leeuwenhoek. Discovered single-celled organisms called "animalcules"
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Define "Cell Theory"
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"Every animal appears as a sum of vital units, each of which bears itself the complete characteristics of life"
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What is histology?
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"Staining" of cells in order to see them
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What do optics do in viewing cells?
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Emphasizes the edges.
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Why is sectioning necessary when viewing cells?
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In order to view cells you need to take a very thin slice of thick tissue.
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Who disproved spontaneous generation of CELLS?
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Louis Pasteur (1800s)
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What did Needham do wrong when trying to (dis)prove Spontaneous Generation?
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His stopper and wax technique were not sufficient to prevent microorganisms from contaminating the sterilized broth.
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What was wrong with Spallanzani's experiment disproving spontaneous generation?
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There was no air exposure to the sterilized broth and life needs air.
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How was Pasteur able to disprove Spontaneous Generation?
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He utilized a swan-neck flask so there was air flow but dust and microorganisms were not able to contaminate the sterile broth.
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Where do cells come from?
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Other cells. Cells divide to produce new cells.
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What did Darwin and Wallace theorize?
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Natural Selection.
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List three characteristics of Natural Selection.
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1. Variation of traits within a population of species.
2. Those traits are heritable. 3. Certain traits allow better survival or reproduction of individuals. |
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Why do ions and polar molecules dissolve in water?
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Hydrogen bonding.
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How strong is hydrogen bonding compared to covalent bonding?
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1/20th the strength
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What 3 things do dissolved molecules do?
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1. Diffuse between parts of a cell.
2. Bump into each other. 3. Undergo chemical reactions. |
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How do cells move things within a cell?
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Diffusion.
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What is in the water in living cells?
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Ions, Minerals, and Carbon-containing compounds.
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Hydrocarbon chains are what, in terms of dissolving in water?
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Hydrophobic
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Oxygen and Nitrogen polarize and are therefore what, in terms of dissolving in water?
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Hydrophilic
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How can a molecule be both hydrophobic AND hydrophilic?
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One end contains a long hydrocarbon chain (hydrophobic) and one end contains a polar end (hydrophilic).
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Describe hydrophobic interactions. Explain why they occur.
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Hydrophobic molecules (or parts) "hide" or try to get as far away from water with other hydrophobic parts. Energetically favorable.
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What are the strongest chemical bonds?
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Covalent bonds.
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List the weak chemical "bonds/interactions" in from strongest to weakest.
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Hydrogen Bonds
Hydrophobic Interactions Van der Waals Interactions |
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What is the energy of motion?
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Kinetic Energy.
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What is the stored ability to cause motion?
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Potential Energy.
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What is released potential energy converted to (drives molecular motion)?
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Heat / Thermal Energy
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Where is energy obtained in the atmosphere to build more complex molecules?
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Solar radiation and electrical energy (lightning).
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Where is energy obtained in the ocean to build more complex molecules?
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Hydrothermal vents.
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Where is energy obtained in rocks to build more complex molecules?
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Radioactive decay.
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What primitive gases were utilized in the Miller-Urey experiment?
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Methane (CH4)
Ammonia (NH3) Hydrogen (H2) Water (H2O) |
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Which more complex molecules were created in the Miller-Urey experiment?
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Hydrogen Cyanide (HCN)
Formaldehyde (H2CO) Amino Acids |
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What value determines whether a reaction is spontaneous?
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Gibbs Free Energy
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What factors into the calculation of Gibbs Free Energy?
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Temperature, energy change (released during reaction), and changes in entropy.
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What types of reactions are "Exergonic"?
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Spontaneous reactions that release Gibbs Free Energy.
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What types of reactions are "Endergonic"?
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Non-spontaneous reactions that absorb Gibbs Free Energy.
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What is the activation energy?
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The energy required to form an intermediate required for a reaction.
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What happens to the energy utilized for activation?
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The activation energy is not stored, but instead is released in the reaction.
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What does a catalyst do?
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Lowers the amount of energy required for activation of a reaction.
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What is an enzyme?
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Biological catalyst.
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What was the first enzyme discovered?
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Diastase (malt to sugar).
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What did Pasteur call enzymes in living cells?
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"Ferments"
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What is the standard ending for enzymes?
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"---ase"
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What is a substrate?
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The reactant on which an enzyme works. (Ex: Sucrose)
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What is an enzyme-substrate complex?
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When the substrate (sucrose) binds to the enzyme (sucrase).
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What is added in order for the substrate to be converted to products?
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H2O
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List the four steps of the enzyme/substrate process.
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1. Substrate binds to enzyme.
2. Substrate converted to products 3. Products released. 4. Active site is available for another molecule of substrate. |
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What type of bonds are present in the "lock and key" binding between molecules?
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Not typically covalent bonds; usually hydrogen bonds and other weak bonds.
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How many substrates can an enzyme break down?
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Lots and lots because the enzyme is not consumed in the reaction.
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What are the four important macromolecules?
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1) Carbohydrates
2) Proteins 3) Lipids 4) Nucleic Acids |
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What are three characteristics of monosaccharides?
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Carbon chains (3-7 C's)
Hydroxyl (-OH) groups Carbonyl group (=O) |
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What is the typical ending for sugars?
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"-ose"
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What is a disaccharide?
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Two linked monosaccharides via a covalent bond.
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What is the formal name for the covalent bond between two monosaccharides?
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Glycosidic Linkage
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What is a polymer made of?
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Chain of monomer subunits.
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What is the name of this reaction:
X-H + Y-OH --> X-Y + H2O |
Dehydration Reaction
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What are the three purposes of polysaccharides?
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1) Store energy
2) Support structures 3) Parts of other macromolecules |
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What stores energy in plants?
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Starch
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What stores energy in animals?
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Glycogen
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What are the four important macromolecules?
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1) Carbohydrates
2) Proteins 3) Lipids 4) Nucleic Acids |
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What are three characteristics of monosaccharides?
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Carbon chains (3-7 C's)
Hydroxyl (-OH) groups Carbonyl group (=O) |
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What is the typical ending for sugars?
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"-ose"
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What is a disaccharide?
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Two linked monosaccharides via a covalent bond.
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What is the formal name for the covalent bond between two monosaccharides?
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Glycosidic Linkage
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What is a polymer made of?
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Chain of monomer subunits.
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What is the name of this reaction:
X-H + Y-OH --> X-Y + H2O |
Dehydration Reaction
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What are the three purposes of polysaccharides?
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1) Store energy
2) Support structures 3) Parts of other macromolecules |
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What stores energy in plants?
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Starch
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What stores energy in animals?
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Glycogen
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What is the reverse reaction of dehydration?
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Hydrolysis
X-Y + H2O --> X-H + Y-OH |
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What does hydrolysis do?
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Breaks down polysaccharides into monosaccharides by adding water.
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What are the monomers in a protein?
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Amino Acids
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What is the center carbon referred to as in an Amino Acid?
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α-Carbon
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At neutral pH what charge does the N have in the amino acid?
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+1
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At neutral pH what charge does one of the O's have in the amino acid?
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-1
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About how many different biological amino acids are there?
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20
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What is a common, but not necessary, ending for proteins?
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"-ine"
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What four categories can the R groups on the amino acids fall into?
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1) non-polar (hydrophobic)
2) polar (hydrophilic) 3) acidic (COO-) 4) basic (NH3+) |
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What is the name of the link between amino acids?
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Peptide bond
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What are linked amino acids called?
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Protein or Polypeptide
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What does the primary structure of a protein refer to?
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Order of amino acids in polymer.
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What end do you start naming a protein from?
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N (amino) terminus --> C (carboxyl) terminus
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What are the two structures for proteins at the secondary level?
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Alpha Helix or Beta Pleated Sheet
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What bonds cause the secondary structures to form?
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Hydrogen bonds
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What causes the folding in the tertiary level?
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All other types of bonds aside from hydrogen: covalent, ionic, van der Waals interactions and hydrophobic interactions
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Almost all enzymes are ____.
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Proteins
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Proteins can be what three things?
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1) Enzymes
2) Structures (blobs, fibers, jellies, etc) ex: collagen, titin 3) Energy source (others proteins, not your own) |
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How are proteins shapes altered?
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Denaturation
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What is denaturation the loss of?
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Secondary, Tertiary, or Quarternary structure
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What causes denaturation?
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Non-peptide bonds are very sensitive to temperature, pH, salt concentration, etc. and may lose their bond given changes in these properties.
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Loss of enzymatic activity is due to changes in the proteins' _____?
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Secondary, Tertiary, or Quarternary structure due to pH/temp/etc change.
(Does not affect primary structure) |
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Hemoglobin is a protein that does what?
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Binds oxygen in blood cells.
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Sickle-cell anemia is caused by what?
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One amino acid difference in hemoglobin.
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What happens to the molecules in sickle-cell anemia?
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Molecules interact and crystallize into a long fiber, changing the shape of the cell. The capacity to cary oxygen is greatly reduced.
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What structure in hemoglobin is influenced by sickle-cell anemia?
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All structures are influenced by the amino acid difference.
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What is an allosteric interaction?
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The binding of an enzyme to "reactant A" is blocked by shape change due to the enzyme binding to "inhibitor B".
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What is found inside of the plasma membrane?
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Intracellular cytoplasm/cytosol.
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What is the cell membrane made up of?
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Plasma membrane and the extracellular cell wall or extracellular matrix.
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Which "macromolecule" contains hydrophobic hydrocarbon chains?
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Lipids
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Why do lipids not follow the typical definition of a macromolecule?
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There are no monomers making up a "polymer".
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Fatty acids and steroids are examples of what?
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Lipids
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The majority of membrane lipids are ____?
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Phospholipids
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What is a phospholipid made up of?
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Hydrophilic head
Hydrophobic tail |
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What is the hydrophilic (polar) head of a phospholipid made of?
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Phosphate linked to one of several polar molecules (glycerol, phosphate, choline)
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What is the hydrophobic (non-polar) tail of a phospholipid made of?
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Fatty acids
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What is a hydrophobic interaction?
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When parts of hydrophobic molecules hide from water near other hydrophobic parts.
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What are the two halves of the plasma membrane/phospholipid bilayer?
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1) Extracellular side
2) Cytoplasmic/cytosol side |
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What do lipids form spontaneously? What is inside/outside of it?
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Cell-like "Liposomes".
Water is inside and outside of the liposome. |
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What are steroids used for?
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Used in membranes and for signaling between cells.
Used for communication via bloodstream. |
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What is the lipid bilayer permeable to?
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Large and small non-polar molecules.
Small polar molecules (including water) |
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What is the lipid bilayer impermeable to?
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Large polar molecules.
Small and large ions. |
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What is osmosis?
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Diffusion of water across a membrane.
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Concentration of solute outside of cells can be what three things?
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1) Isotonic
2) Hypotonic 3) Hypertonic |
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Isotonic implies the concentration of a solute is what outside of the cell?
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The concentration of the solute is the same outside and inside of the cell.
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Hypotonic implies the concentration of a solute is what outside of the cell?
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The concentration of the solute is lower outside of the cell.
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Hypertonic implies the concentration of a solute is what outside of the cell?
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The concentration of the solute is higher outside of the cell.
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Sea water is an example of what sort of concentration situation?
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Isotonic (concentration is equal outside/inside of cell)
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Fresh water is an example of what sort of concentration situation?
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Hypotonic (concentration is lower outside of cell)
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Evaporated sea water is an example of what sort of concentration situation?
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Hypertonic (concentration is higher inside of cell)
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Which solute concentration is ideal for an animal cell, and why?
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Isotonic because water is diffusing in and out of the cell. There is not a solid cell wall to hold water if it didn't leave; the cell would shrivel up if water only left.
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Which solute concentration is ideal for a plant cell?
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Hypotonic because water is diffusing into the cell, but not leaving. The strong cell wall becomes "turgid" whereas if water was leaving the cell would be "flaccid" or "plasmolyzed".
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If you put a micro-organism in a solution with lots of sugar, the organism will do what? Why?
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Shrivel up because there is a high concentration outside of the cell which implies hypertonic. Hypertonic situations make cells shrivel.
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Cells in fresh water (hypotonic) utilize what two things to prevent breaking?
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1) Stiff cell wall external to cell membrane (Turgor Pressure)
2) Contractile Vacuole |
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What does "Turgor Pressure" mean in regards to plant cell walls?
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The force directed against a plant cell wall after the influx of water and swelling of the cell due to osmosis.
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When the plasma membrane pinches and capture a substance from outside of the cell to bring inside this is called?
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Endocytosis
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When fusion releases the vesicle contents outside of the cell, this is called?
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Exocytosis
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Endocytosis pinches off the plasma membrane and contents outside of the cell to create what?
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Vesicle
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What can control membrane permeability?
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Proteins
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What is a transmembrane protein?
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A protein that spans across an entire phospholipid bilayer that has hydrophilic ends and a hydrophobic center that is embedded in the membrane.
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In which way can lipids move around in the phospholipid bilayer?
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Sideways, but they can't switch sides.
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Facilitated diffusion can take place in what two ways?
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1) Via a channel or pore
2) Via carrier proteins |
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Facilitated diffusion flows in what concentration direction?
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High concentration to low concentration.
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What type of proteins open on one side, allow the solute to enter, then the other side opens and the solute leaves?
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Carrier Proteins
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When going with the diffusion gradient (high to low) where does the energy come from?
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Natural diffusion process.
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Active transport goes in which direction for concentration?
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Low concentration to high concentration.
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There are two methods to obtain the energy necessary for active transport. What are they?
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1) Cotransport
2) Chemical Reaction |
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What is cotransport?
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An active transport method where diffusion of one molecule (high-->low) drives active transport of the second (low-->high).
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Which chemical reaction provides energy for active transport?
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ATP --> ADP + P
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What are the three parts of a nucleotide?
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Nitrogenous base (A, T, U, G, or C)
Phosphates (1-3) Monosaccharide (sugar - ribose or deoxyribose) |
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What is ATP made up of? Base=? Sugar=? What else?
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Base = adenosine
Sugar = ribose 3 Phosphates |
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How does ATP provide energy?
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By breaking one phosphate bond provides energy to cells (causes major shape changes)
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Where does the energy to make ATP come from?
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Catabolic reactions that are exergonic.
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ATP hydrolysis provides energy for what?
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Cellular processes that are endergonic.
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What does the arrangement of nucleotide monomers provide the code for?
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Making proteins.
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What 3 things did Darwin know about Natural Selection?
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1) variation of traits within a population
2) traits are heritable 3) certain traits promote survival |
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What 2 things didn't Darwin know about Natural Selection?
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1) why there was variation
2) how inheritance worked |
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What three conflicts were there in Darwin's time with "stable heredity"?
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1) spontaneous generation of organisms
2) preformation 3) inheritance of acquired traits |
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What was the idea behind "preformationism"?
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A complete and very small version of organism offspring (for endless generations) was found in sperm or eggs.
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What were some problems with "preformationism"?
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- Russian Dolls (how small can they get...)
- Single-celled life? - Where did variation of traits come from? - How could changes during development be accounted for? |
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How did Mendel come up with his rules for sexual inheritance of traits?
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He picked simple traits to study, utilized easily-bred organisms, used large numbers and probabilities.
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How were Mendel's ideas initially accepted?
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They weren't; he was completely ignored because nothing in cells related to his probabilities.
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Why did people think genes were proteins?
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- Many different proteins with different activities
- DNA had about equal concentrations of four nucleotides (A, C, G, T) |
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What was the old DNA model called?
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Tetranucleotide model.
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What are three characteristics of Eukaryotic cells?
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1) Internal membranes (bound nucleus w/ DNA)
2) Most have sexual reproduction 3) Many other organelles with membranes |
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What are four characteristics of a typical Prokaryote Bacterium?
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1) DNA in cytoplasm (no membrane)
2) No internal membranes/organelles 3) No sexual reproduction (no sperm, eggs, fertilization) 4) Cell division to make "offspring" |
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Viruses are not cells (or dead/alive), so how do they infect?
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Attaches to a cell which it infects to produce more virus.
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What does a virus contain?
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Proteins and nucleic acids.
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What is a bacteriophage, or just phage?
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A bacteria that has been infected by a virus.
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Which experiment focused on radioactive labeling?
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Hershey-Chase Experiment.
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In the Hershey-Chase Experiment, proteins were labeled with what?
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Radioactive label of the 35 S in amino acid methionine.
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In the Hershey-Chase Experiment, DNA was labeled with what?
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Radioactive label of the 32 P in phosphates.
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In the Hershey-Chase Experiment what two observations were made that demonstrated that DNA was the source of heredity and genetic material?
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1) Virus proteins labeled w/ 35 S stayed outside of the cell, can be washed off
2) Virus DNA labeled w/ 32 P got inside of the cells, cannot be washed off |
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In Chargaff's analysis of DNA, what pattern did he discover?
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% Adenine = % Thymine
% Cytosine = % Guanine |
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What did Linus Pauling discover?
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Protein Alpha Helix
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Maurice Wilkins and/or Rosalind Franklin were experts on which technology that helped determine the structure of DNA?
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X-Ray Crystallography.
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James Watson and Francis Crick are given credit for what?
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Solving DNA structure mystery.
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How does one conduct x-ray crystallography?
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1) make solid DNA crystal
2) shine x-rays 3) scatter pattern gives structural information -- width of helix -- what's inside, etc. |
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How are nucleotide bases linked?
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Covalent bonds.
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Which bases are pyramidines?
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T/C (1 ring)
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Which bases are purines?
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A/G (2 rings)
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How are the bases bonded together?
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Hydrogen bonds.
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What is base pairing?
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Nucleotides (bases) on one strand H bonds to complementary nucleotides on other strand.
-- T & A -- C & G (Explains Chargoff's Rule) |
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Which direction do the strands of DNA run in?
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5' end --> 3' end which results in the two strands running in opposite directions. (Suggests copying mechanism)
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Which is the correct model for DNA replication?
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Semi-Conservative Model
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Which model does this describe for DNA replication:
Parent strand makes two new strands (half parent / half daughter - 50/50) New 50/50 strands create 2 more 50/50 models and 2 entirely new strands. |
Semi-Conservative Model
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Which model does this describe for DNA replication:
Parent strand makes an entirely new strand and maintains 100% of the parent strand. |
Conservative Model
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Which model does this describe for DNA replication:
Each strand of both daughter molecules contains a mixture of old and newly synthesized parts. |
Dispersive Model
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How did scientists confirm the Semi-Conservative Model of DNA replication?
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Used DNA with different isotopes of Nitrogen. Original DNA = denser; newly synthesized DNA = less dense.
All DNA of intermediate density (1st replication); some DNA of intermediate and some of lighter density (2nd replication). |
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Which proteins separate and unwind the strands of DNA during replication?
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Helicase and Topoisomerase
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Why are helicase and topoisomerase required for DNA replication?
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They stabilize exposed, separated, and unwounded strands by binding.
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Which enzyme/protein adds/links new nucleotides into the new strand during DNA replication?
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DNA Polymerase
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Since DNA Polymerase requires something to bond to in order to begin replicating DNA, where does the beginning of the strand come from?
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Primase builds an RNA "primer" at the beginning of the DNA replication, to which DNA Polymerase begins adding DNA nucleotides in the 5' --> 3' direction.
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What protein/enzyme replaces the RNA "primer" with DNA nucleotides?
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A different DNA Polymerase than the one adding/linking the DNA nucleotides to the strand.
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Since DNA Polymerase only adds nucleotides in one direction (free 3' end) how does the opposite side catch up?
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Replication on one strand keeps re-starting on newly exposed strand creating Okazaki fragments.
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What is the problem with having replication re-starting on the newly exposed strand? What enzyme fixes this issue?
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This re-starting generates many fragments (Okazaki fragments) which are joined (ligated) by DNA Ligase.
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What is the shape of Eukaryotic chromosomes?
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Linear
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What is the shape of Prokaryotic chromosomes?
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Circular
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Why can't the ends of eukaryotic chromosomes be replicated?
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The chromosomes are linear and DNA polymerase needs room on the 5' end to replace the RNA primer.
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What is the problem with Eukaryotic chromosomes being linear?
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The molecules become shorter and shorter as DNA polymerase is unable to replace the RNA primer on the ends of the strands.
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What is telomere?
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End of chromosome that helps deal with the issue of shorter and shorter strands.
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What does telomerase do?
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Enzyme that makes longer telomeres.
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What types of "immortal" cells is telomerase made in? (3)
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1) Germ line cells
2) Stem cells 3) Cancer cells |
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What is the name for alterations in DNA?
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Mutations
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What is it called when a small number of nucleotides are altered or removed?
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Point Mutation
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How can small mutations be corrected?
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DNA polymerase can "proofread" the strand using the other strand.
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If big mutations that affect both strands of the DNA occur, what can be done?
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Double-stranded break repair; repairs using replicated DNA or in eukaryotes, second "homologous" chromosome.
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Where is the site where DNA strands start to separate?
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Origin of Replication
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When DNA is unzipped (by helicase), replication forks form what?
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Replication bubble.
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How are prokaryotes distinguished from eukaryotes? (3)
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- No nucleus (vs. nucleus present)
- Circular DNA (vs. linear) - One origin of replication (vs. many) |
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What is the significance of a triplet of nucleotides?
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Codon - region that codes for one amino acid.
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Where does mRNA come from?
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Transcription of DNA.
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How is transcription different from DNA replication?
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- RNA is single-stranded
- Uses U instead of T - Requires RNA Polymerase instead of "primer" |
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What is the purpose of RNA Polymerase?
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It holds the DNA open for transcription and then puts it back together. Begins transcription of RNA from DNA. Builds single-stranded RNA from complementary DNA template strand.
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What is being described?
Large, stable rRNAs assembled with proteins into dense particles. |
Ribosomes
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Ribosomes contain how many subunits? What are they differentiated?
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2: large and small
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Ribosomes / rRNA (ribosomal RNA) are the site for what?
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Protein Synthesis
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What gets information from DNA in nucleus and then goes to the ribosome in cytoplasm?
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Messenger RNA (mRNA)
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When is mRNA created?
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During transcription
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What does "pre-mRNA" go through to become mRNA?
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RNA processing
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What is: "making DNA from DNA template" ?
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Replication
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What is: "making RNA from DNA template" ?
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Transcription
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What is: "making protein from mRNA template" ?
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Translation
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During transcription in prokaryotes, what convenient action can take place due to the lack of a nucleus?
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Ribosomes attach themselves to mRNA as it's being transcribed.
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What are polyribosomes?
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Many ribosomes attached to the same mRNA strand.
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What were the "adaptors" in Crick's "Adaptor" Hypothesis?
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Transfer RNA (tRNA)
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What is transfer RNA (tRNA)?
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70-80 nucleotides long that matches specific amino acids with specific mRNA triplet codons through base pairing.
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How does tRNA obtain its clover-leaf-esque shape?
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Hydrogen bonds between base pairs on the molecule interact and form it into its shape.
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What are the three specific bases on tRNA called when they bind with 3 corresponding bases on the mRNA?
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Anti-codon (tRNA)
Codon (mRNA) |
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What enzyme/protein is used to attach an amino acid to its corresponding tRNA?
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Aminoacyl tRNA Synthetase
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What is used to link amino acids attached to tRNAs to the protein chain?
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Ribosome
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Ribosomes have how many slots abbreviated as?
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3 - EPA
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What energy source does translation use?
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GTP
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What type of RNA makes the ribosome - the machine for making proteins?
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Ribosomal RNAs
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What type of RNA is transcribed from DNA and then translated into protein chains at a ribosome?
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Messenger RNA
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What type of RNA brings amino acids to the ribosome - carries a specific amino acid and specific anti-codon that binds to the mRNA codon?
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Transfer RNA
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How is the problem of deciding where to begin the correct "reading frame" fixed?
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Specific start codon - AUG - methionine. All proteins start with the first (5') methionine.
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What are UTRs?
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Untranslated Regions - two ends of mRNA often do not contain information for making a protein.
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Stopping translation occurs when?
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When the ribosome comes along one of three nonsense "stop" codons: UAG, UAA, UGA.
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What happens when a stop codon is reached?
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They do not bind to tRNA, instead binds protein "release factor" which releases protein.
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Which end of the protein is made first?
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Amino (5') to carboxyl (3')
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How many proteins are made from a single strand of DNA for Prokaryotes? for Eukaryotes?
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Prokaryotes: several consecutive proteins.
Eukaryotes: one type of protein. |
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What happens at the "promoter DNA"?
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RNA polymerase binds and transcription starts here.
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What happens at the "terminator DNA"?
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This is where transcription ends.
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What two steps occur during mRNA processing in eukaryotes?
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1) Removal of non-coding introns
2) 5' and 3' ends modified |
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Pre-mRNA is made up of what two parts.
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Introns and Exons
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Which portion of the mRNA is removed during mRNA processing?
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Introns
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What molecule removes introns during mRNA processing?
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Spliceosome - complex of proteins and small nuclear RNAs (snRNA)
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Describe the concept of "alternative splicing".
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Performed by some eukaryotic mRNAs to keep different exons; leads to different mRNA and ultimately different proteins.
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What is added to the 5' end of mRNA during mRNA processing?
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Capping G-P-P-P
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What is added to the 3' end of mRNA during mRNA processing?
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Poly-A tail (a long stretch of A's)
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Why are the 5' and 3' ends of mRNA modified during mRNA processing?
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Helps stabilize RNA, export RNA from nucleus, and attach RNA to ribosomes.
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Gene expression is based on what two things?
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Whether a cell makes a protein, and how much it makes of that protein.
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What things are used to control transcription of mRNA from DNA?
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Transcription factors
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Transcription factors bind to nearby DNA and can either ___ or ___?
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Promote or Inhibit
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What two portions make up the "Promoter" site on DNA?
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1) Place where RNA polymerase binds
2) Operator |
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What does the operator do?
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Controls the access of RNA polymerase to the genes
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What does the operon include in a prokaryotic cell?
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Promoter, operator, and genes.
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What molecule can block off the operator and prevent DNA transcription from being carried out?
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Repressor
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What binds in a repressor to make it available to block the operator?
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Corepressor
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What is the corepressor?
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The molecule that, as it accumulates, binds to the repressor, making it active, which goes on to block the operator and prevent transcription.
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When the cell has enough of a substance it will stop making the enzymes that create the substance. What is this called?
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Negative feedback
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The steady state the body likes to maintain.
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Homeostasis
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In contrast with repressors/corepressors, lac operon is an example of what two enzymes?
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Inducer (allolactose) which binds to an Inactive Repressor (which no longer fits in the operon).
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Transcription factors can fit into two categories. Name them.
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1) stimulate transcription (bind to enhancer DNA)
2) repress transcription (bind to silencer DNA) |
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If enhancer and silencer DNA are distant from the promoter, how can they affect transcription?
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DNA-bending proteins may fold DNA into such a shape that the enhancer or silencers are right across from the promoter.
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What kind of proteins can modify wrapping of DNA?
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Histone proteins.
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Nucleosomes are made how?
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By DNA looping around histones.
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Histones that form huge conglomerations of DNA negatively affect which process?
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Transcription
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What kinds of histone modification take place to make DNA more accessible for transcription?
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Acetylation (spreads histones out)
(Methylation) |
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Gene expression is more complex in which type of cells?
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Eukaryotes
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Gene expression modifies which step of production of proteins?
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Any step!
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There are four types of mutations that can occur...
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1) No effect (multiple codes for a single amino acid)
2) Missense (codes for wrong codon --> wrong amino acid) 3) Nonsense (codes for stop codon - premature end) 4) Frame Shift (add an extra nucleotide) |
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What is a "conservative" mutation?
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When an amino acid substitution is insignificant due to the amino acid having similar properties to the one it is replacing.
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