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167 Cards in this Set
- Front
- Back
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DNA is the
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instructions (program) that tells the cell what to do.
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what do the instructions in the DNA do?
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Make protiens
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The study of metabolic defects provided evidence
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that genes lead to proteins.
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Archibald Garrod in 1909
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The study of metabolic defects provided evidence that genes lead to proteins.
suggested that some metabolic disorders were caused by a blocked pathway. -inherited diseases were the result of the lack of an enzyme |
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blockage in a pathway not only stops the production of something we need but it also may lead to
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the accumulation of something we don’t want.
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the biochemical pathway for synthesis of the amino acid arginine involves
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two steps
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George Beadle and Edward Tatum conducted experiment with bread mold,
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Neurospora crassa, and demonstrated that different mutants (generated by X-rays) had the pathway of arginine (an amino acid) synthesis blocked at different steps.
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The suggestions of Garrod were confirmed in the
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1930's
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Beadle and Tatum deduced that the 3 different mutant types each lacked a different
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enzyme in the pathway which synthesizes arginine.
From these results they formulated the one gene-one enzyme hypothesis |
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genes are responsible for?
if it is messed up it causes? |
protiens
metobolic disorder |
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single most important thing ever
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DNA ==> RNA ==> Proteins
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DNA to RNA
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This process is called transcription.
---Transcription is the synthesis of RNA using DNA as a template |
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The RNA is ________ to DNA
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complementary to the DNA
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RNA that is synthesized from a gene coding for a protein is called
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messenger RNA (mRNA), or a transcript
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Differences between DNA and RNA:
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1. sugar - deoxyribose (DNA) verses ribose (RNA)
2. base - thymine (DNA) is replaced by uracil (RNA) |
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DNA ribose is
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missing an O RNA has O, this is what makes them a diff sugar from one another ->deoxyribose (DNA) verses ribose (RNA)
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During transcription of a gene, only one
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strand (template strand) of the DNA’s two strands is read
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Different genes use different
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strands as the template strand.
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step two of DNA transcription
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RNA to protein
This process is called translation. ---Translation is the synthesis of a polypeptide (protein) directed by mRNA |
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Why is the second process of transcription called translation?
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Converting the language of nucleic acids into the language of proteins:
reading nucleotide languge and convert them to amino acid language ->protiens 4 bases in nucleic acids 20 amino acids in proteins |
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Translation occurs on the
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ribosomes
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During translation, proteins are synthesized according to the genetic message of
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sequential codons in the mRNA.
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Codon
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is a three-nucleotide sequence! in mRNA that specifies which amino acid will be added to a growing polypeptide or signals the termination of translation.
3 nucleotide sequence and it encodes for a single amino acid |
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transfer RNA (tRNA) and ribosomal RNA (rRNA) act as the
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"interpreter" between the nucleotide “language” of mRNA and the amino acid “language” of proteins.
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In the genetic code, a triplet of nucleotides specifies
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an amino acid
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There are 4 nucleotides in
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RNA and 20 amino acids.
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-4 different nucleotides in RNA combining to make ______ which are
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Codons, which are 3-nucleotides sequences
Math would dictate that there could potentially be as many as 64 amino acids But there are only 20, since each amino acid is usually encoded by more than one codon. each codon is encoded for one amino acid, but most amino acids contain more than one codon (overlapping, and creating the same) |
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60 of the 64 possible codons code for
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amino acids. The remaining four codons signal the translation to start (start codon) and translation to stop (stop codon
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Since there are only 20 amino acids, more than
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one codon can code for the same amino acid.
This relationship makes the code redundant, or degenerate. |
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The codons usually differ only at the
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third position.
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There is no _______ iin the triplet code since a given triplet codes for one and only one amino acid.
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ambiguity
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Why are only 20 amino acids formed from the 64 possible combinations of the bases?
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An amino acid can be encoded by more than one nucleotide triplet.
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RNA polymerase binds to the
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promoter region of DNA near the beginning of a gene, separating the double helix near the promoter.
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RNA polymerase travels along the
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DNA template strand, catalyzing the addition of ribose nucleotides into an RNA molecule.
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The nucleotides in the RNA are complementary
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to the template strand of the DNA.
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At the end of a gene, RNA polymerase encounters a sequence of DNA called a
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termination signal.
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RNA polymerase detaches from the DNA and releases the
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RNA molecule.
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After termination, the DNA
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completely rewinds into a double helix.
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Conclusion of transcription
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The RNA molecule is free to move from the nucleus to the cytoplasm for translation, and RNA polymerase may move to another gene and begin transcription once again, or it can even re-bind the same promoter and transcribe the same gene again.
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What is the order of steps in the transcription process?
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Initiation, elongation, termination
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How does initiation begin?
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2. RNA polymerase finds a promoter region and binds, causing the DNA double helix to unwind.
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If the mRNA transcript AUGCGCUGCAAU were to leave the nucleus and undergo translation at a ribosome, what would be the sequence of anticodons translating this nucleotide into protein?
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4. UACGCGACGUUA
because A=U C=G |
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Translation is the
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RNA-directed synthesis of proteins.
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During translation, proteins are synthesized according to the
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genetic message of sequential codons in the mRNA.
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The sequence of nucleotides present in the DNA is reflected by the
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sequence in the mRNA
AND The sequence of nucleotides in a mRNA determines the sequence of amino acids. AND The sequence of amino acids determines the protein. |
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a mutation changes the
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sequence of mRNA which determines sequence of Amino Acids wich determines the proteins
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where proteins are built.
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ribosome
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The ribosome coordinates the pairing of
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tRNA anticodons with mRNA codons
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ribosomes are composed of
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ribosomal RNA (rRNA) and protein
-The subunits combine as a ribosome only when they are translating a protein |
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The P site of a ribosome
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holds the tRNA with the polypeptide chain attached.
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The A site of a ribosome
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hold the tRNA with the next amino acid to be added.
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catalytic site
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forms the peptide bond
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The ribosome holds all the components together as enzymes transfer the
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next amino acid to the growing polypeptide chain.
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Where does protein synthesis occur?
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On the ribosomes outside the nucleus
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As in transcription, translation (protein synthesis) occurs in three stages:
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1. Initiation
2. Elongation 3. Termination |
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tRNA acts as the
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"interpreter" between the nucleotide “language” of mRNA and the amino acid “language” of proteins.
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anticodon portion of the tRNA
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“interpreter,” the tRNA must “read” the mRNA
The other portion the tRNA’s role as “interpreter” is to transfer the correct amino acid from the cytoplasmic pool of amino acids to the ribosome for protein synthesis. |
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for every codon there is
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one anti-codon, one amino acis,
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Using this one codon => one anticodon => one amino acid method the gene
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decoded to synthesize a protein.
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Start Codon
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almost always a thymine, AUG, is where initiation begins
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The initiation complex binds to an
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mRNA molecule
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The methionine (met) tRNA anticodon (UAC) base-pairs with the
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start codon (AUG) of the mRNA.
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Elongation
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The next tRNA occupies the A site and the anticodon hydrogen bonds to the codon of the mRNA.
peptide bond the methionine from the initiator tRNA forms a peptide bond with the amino acid on the tRNA at the A site. this leaves the tRNA at the P site with no amino acid, and the tRNA at the A site with a dipeptide attached. |
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Translocation
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the tRNA vacates the P site
dont know much about it, ribosomes will move one codon down |
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Translocation
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the tRNA vacates the P site
the ribosome moves one codon down the mRNA. This translocates the tRNA (with the growing peptide) from the A site to the P site |
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Termination
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The mRNA reaches a stop codon: UAA, UAG, or UGA
---Stop codon is a triplet codon that signals the end of translation. |
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-Mutations
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are permanent changes in the DNA that can involve large chromosomal regions or a single nucleotide pair.
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Point mutations
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are mutations limited to one or two nucleotides in a single gene, and can affect the function of a protein.
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Substitutions
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are the replacement of one base with another
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Insertion
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is the insertion of one or more nucleotide pairs into a gene
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Deletion
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is the deletion of one or more nucleotide pairs from a gene
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Ionizing Radiation
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Radiation can cause a process called ionization in our DNA.
Causes DNA molecules to lose or gain electrons, resulting in the breaking apart of our DNA, and re-arrangement of bases (mutations). X-rays can cause radiation damage. But the radiation from x-rays cannot pass through lead. This is why a lead apron is used during x-rays. Ultraviolet radiation from the sun can have the same effect, and this radiation is blocked by sunscreen. |
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Elongation
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The next tRNA occupies the A site and the anticodon hydrogen bonds to the codon of the mRNA.
Peptide bond formation the methionine from the initiator tRNA forms a peptide bond with the amino acid on the tRNA at the A site. this leaves the tRNA at the P site with no amino acid, and the tRNA at the A site with a dipeptide attached. |
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protien 2o amino acids long how many codons? how many nucleotides?
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20 codons
3x20=60 nucleotides |
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first three nucleotides is
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a codon
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ultamite goal of translation?
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to make protiens
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ribsomes are made of
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ribosomal RNA and protien
RNA doesnt do anything else but make ribosomes |
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The main ideas of evolution were not widely accepted until after
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Charles Darwin published On the Origin of Species in 1859
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Evolution
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is a change in the genetic makeup of a population over time as a result of natural selection
takes alot of time, but it depends on how quickly things reproduce |
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Plato
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(427–347 B.C.) proposed that each object on Earth was merely a temporary reflection of its divinely inspired “ideal form”
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Aristotle
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(384–322 B.C.) arranged all organisms on a linear scale of increasing complexity (the “ladder of Nature”)
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So how did the concept of Evolution come about?
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Exploration of new lands revealed a staggering diversity of life
Early explorers often took naturalists along to catalogue the plant and animal life they found The number of species was far greater than expected The vast numbers of species observed allowed naturalists to see patterns that had not emerged before Each area had its own distinctive set of species Some species closely resembled one another yet differed in some characteristics These patterns seemed inconsistent with the idea that species were fixed and unchanging |
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Fossils
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the preserved remains or traces of organisms that died long ago
Fossils revealed that life has changed over time Discovered in many forms: Petrified remains of bones, wood, shells, or their impressions left in mud Most are found in sedimentary rock William Smith, a British surveyor, recognized that certain fossils were always found in the same layers of rock Many rocks occur in layers, with newer layers positioned over older layers Also, the organization of fossils and rock layers was consistent with fossils of a given type always in the same layers Most fossils found in the oldest layers were very different from modern organisms The resemblance to modern organisms gradually increased in progressively younger rocks Many of the fossilized species were extinct |
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The fossil evidence led to a revolutionary conclusion:
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Different types of organisms had lived at different times in the past
This countered the view that species were created at one time and did not change afterwards |
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Some scientists devised non-evolutionary explanations for fossils :
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o account for the existence of extinct species while preserving the notion of a single creation by God, Georges Cuvier (1769–1832) proposed the theory of catastrophism
High numbers of species were created originally A series of catastrophes produced rock layers and destroyed many species, preserving some as fossils Modern day species are the survivors of these catastrophes but it didnt explain why we have as many species of animals that were very closly related |
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Geological evidence led to several conclusions:
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Earth is far older than the 6,000 years proposed by theologians
There was enough time for evolution to occur Modern geologists estimate that the Earth is about 4.5 billion years old |
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Charles Darwin and Alfred Russel Wallace proposed a mechanism of evolution
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By the mid-1880s, a growing number of biologists had concluded that present-day species had evolved from earlier ones
But how? 1858, Charles Darwin and Alfred Russel Wallace independently provided evidence of the occurrence of evolution and proposed the mechanism for how it occurs |
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Darwin and Wallace had both had traveled extensively and studied plants and animals in detail
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Both had observed that some species differ in only a few traits
Both knew that fossils showed a trend of increasing complexity Both were aware that the Earth is extremely old |
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Darwin and Wallace independently proposed that organisms evolved by
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natural selection
Both presented papers to a biological journal in London in 1858 Darwin published On the Origin of Species by Means of Natural Selection in 1859 |
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descent with modification
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Individuals in each generation differ slightly from the members of the preceding generation
Over long time periods, small genetic differences accumulate to produce major transformations |
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Principle 1
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Individual members of a population are different from one another.
We now know that variations arise purely by chance resulting from random mutations in DNA The differences are obvious in many physical characteristics and extend to the molecular level |
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Principle 2:
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At least some of the differences between members of a population are characteristics that may be passed from parent to offspring
However, the mechanism of inheritance was not understood at this point in time |
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Principal 3:
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In each generation, some individuals in a population survive and reproduce successfully. Others do not
Darwin observed that many more individuals are born than survive to reproduce. Some individuals have more offspring than others. |
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Principle 4:
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Individuals with advantageous traits survive longest and produce the most offspring, a process known as natural selection
In the competition to survive and reproduce, winners are determined not by chance but by the traits they possess |
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what two things is needed for natural selection/evolution
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variation and competion
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Principle 4
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Individuals with advantageous traits survive longest and produce the most offspring, a process known as natural selection
In the competition to survive and reproduce, winners are determined not by chance but by the traits they possess |
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Natural selection modifies
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populations over time
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Natural selection acts on individuals within a population; however, it is the
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population that changes over time
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An individual cannot evolve
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but a population can
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How Do We Know That Evolution Has Occurred?
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An overwhelming body of evidence in multiple areas of science supports the theory of evolution
1. Fossils provide evidence of evolutionary change over time 2. Comparative anatomy gives evidence of descent with modification 3. Embryological similarity suggests common ancestry 4. Modern genetic analyses reveal similarities among diverse organisms |
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Fossils provide evidence of evolutionary change over time
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Several series of fossils have been found that exhibit the evolution of body structures over time
One series reveals that modern whales evolved from land-dwelling ancestors |
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Comparative anatomy gives evidence of descent with modification
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Comparing the bodies of organisms of different species has revealed differences that could result only from evolutionary change during descent from a common ancestor
-- Homologous structures provide evidence of common ancestry Homologous structures are structures that have the same evolutionary origin despite their current appearance or function Bird and mammalian forelimbs are homologous structures The forelimbs are used for flying, swimming, running, and grasping Despite their different uses, they have strong anatomical similarities Such similarity is exactly what we would expect if bird and mammal forelimbs were derived from a common ancestor |
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Bird and mammalian forelimbs are
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homologous structures
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Embryological similarity suggests common ancestry
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All vertebrate embryos resemble one another in their early development
All vertebrate embryos possess genes that direct development of gill slits and a tail Adult fish retain gills and tail because the genes are active throughout their embryonic development Humans are born without gills and a tail because the genes are active only during early embryonic development |
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Modern genetic analyses reveal similarities among diverse organisms
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All organisms share related biochemical processes
All cells use DNA as a genetic blueprint All use RNA, ribosomes, and approximately the same genetic code for translation All use roughly the same set of 20 amino acids to build proteins All use ATP to transfer energy Striking genetic similarities between organisms imply evolutionary relationships. Controlled breeding modifies organisms |
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Artificial selection
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is selective breeding to produce plants and animals that possess desirable traits
Modern dogs are descended from wolves In only a few thousand years, humans artificially selected for all breeds of modern dogs |
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Humans have created tremendous variation in several species over relatively short periods of time through
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artificial selection
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Every pesticide
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in existence has fostered a resistance in at least one of the insect species it is designed to kill
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Genes
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are sequences of nucleotides at specific locations on chromosomes
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Inheritance
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is the process by which the characteristics are passed on to offspring
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A GENE
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is a unit of DNA that encodes information needed to produce proteins, cells, and entire organisms
Can be a few hundred to many thousands of nucleotides in length |
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The location of a gene on a chromosome is called its
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locus (plural, loci)
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In the ordinary body cells (not sperm or eggs) of many organisms the chromosomes occur in
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pairs.
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Each species has a characteristic number
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of chromosomes and the individual
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Human cells contain __chromosomes and __ pairs
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46 chromosomes, 23 pairs
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Humans: Autosomes _____ and ____ od sex chromosomes
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(22 pairs)
1 pair |
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Autosomes
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are the non-sex chromosomes
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Genes are sequences of
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nucleotides at specific locations on chromosomes
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Homologous chromosomes carry the same
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kinds of genes for the same characteristics
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Genes for the same characteristic are found at the same
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loci on both homologous chromosomes
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Homologous chromosomes (homologues) are a pair of
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chromosomes that contain the same genes.
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Genes for a characteristic found on homologous chromosomes may not be
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identical
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Alternative versions of genes found at the same gene locus are called
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alleles
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Alleles are formed by
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mutations
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Alleles are formed by mutations
If a mutation occurs in gametes |
the cells that become sperm or eggs, then the mutation can be passed on from parent to offspring
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An organism’s two alleles may be the
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same or different
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Each cell carries ___ alleles per characteristic, one on each of the two ___________.
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two
homologous chromosomes |
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If both homologous chromosomes carry the same allele (gene form) at a given gene locus, the organism is _________
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homozygous at that locus
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If both homologous chromosomes carry the ____ allele (gene form) at a given gene locus, the organism is homozygous at that locus
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same
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If two homologous chromosomes carry different alleles at a given locus, the organism is
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heterozygous at that locus, also called hybrid.
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The Relationship Among Genes, Alleles, and Chromosomes
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How Were the Principles of Inheritance Discovered?
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Gregor Mendel - Austrian monk in a monastery in the late 1800s
--Discovered patterns of inheritance and many essential facts about genes, alleles, and the distribution of alleles in gametes during sexual reproduction He chose edible pea plant for his experiments Allowed him to see patterns in the way plant characteristics were inherited |
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Why Pea plants?
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Pea flowers have stamens, the male structures that produce pollen. Pollen contains the sperm (male gametes); sperm are gametes and pollen is the vehicle
Pea flowers have carpels, female structures housing the ovaries, which produce the eggs (female gametes) Pea flower petals enclose both male and female flower parts and prevent entry of pollen from another pea plant |
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Because of their structure, pea flowers naturally
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self-fertilize
Pollen from the stamen of a plant transfers to the carpel of the same plant, where the sperm then fertilizes the plant’s eggs |
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Mendel was able to mate two different plants by
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(cross-fertilization)
Female parts (carpels) were dusted with pollen from other selected plants |
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The key to Mendel’s success:
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He chose a simple experimental design
He chose to study individual characteristics (called traits) that had unmistakably different forms, such as white versus purple flowers He started out by studying only one trait at a time He followed the inheritance of these traits for several generations, counting the numbers of offspring with each type of trait By analyzing these numbers, he saw the basic patterns of inheritance emerge |
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Pea plants that are homozygous for a particular characteristic always produce
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the same phenotype
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Pea plants that are _______ for a particular characteristic always produce the same phenotype
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homozygous
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How Are Single Traits Inherited?
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Pea plants that are homozygous for a particular characteristic always produce the same phenotype
If a plant is homozygous for purple flowers, it will always produce offspring with purple flowers Plants that are homozygous for a characteristic are described as true-breeding |
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If a plant is homozygous for purple flowers, it will always produce
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offspring with purple flowers
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Plants that are homozygous for a characteristic are described as
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true-breeding
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the mating of pollen and eggs (from same or different parents)
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A genetic cross
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1rst part of hypothesis explains the ingeritance of single traits
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Each trait is determined by pairs of genes; each organism has two alleles for each gene, one on each homologous chromosome
True-breeding white-flowered plants have different alleles than true-breeding purple-flowered plants |
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2nd part of hypothesis explains the ingeritance of single traits
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When two different alleles are present in an organism, the dominant allele may mask the recessive allele, even though the recessive allele is still present
In edible peas the purple-flower trait is dominant to the white-flower trait |
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3rd part of hypothesis explains the ingeritance of single traits
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The pairs of alleles on homologous chromosomes separate, or segregate, from each other during meiosis, which is known as Mendel’s law of segregation
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4rth part of hypothesis explains the ingeritance of single traits
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Chance determines which allele is included in a given gamete—because homologous chromosomes separate at random during meiosis; the distribution of alleles to the gametes is also random
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5th part of hypothesis explains the ingeritance of single traits
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True-breeding organisms have two copies of the same allele for a given gene and are homozygous for that gene; hybrid organisms have two different alleles for a given gene and are heterozygous for that gene
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The particular combination of the two alleles carried by an individual is called the
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genotype
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The physical expression of the genotype is known as the
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phenotype (for example, purple or white flowers)
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The probabilities of each combination (and therefore the fraction each genotype is of the total offspring) are
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1/4 PP, 1/2 Pp, and 1/4 pp
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The Punnett square method
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predicts offspring genotypes and phenotypes from combinations of parental gametes
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decribe the punnett square method
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1. Assign letters to the different alleles of the characteristic under consideration (uppercase for dominant, lowercase for recessive)
2. Determine the gametes and their fractional proportions (out of all the gametes) from both parents 3. Write the gametes from each parent, together with their fractional proportions, along each side of a 2 x 2 grid (Punnett square) 4. Fill in the genotypes of each pair of combined gametes in the grid, including the product of the fractions of each gamete (e.g., 1/4 PP, 1/4 Pp and 1/4 pP, and 1/4 pp) 5.Add together the fractions of any genotypes of the same kind (1/4 Pp + 1/4 pP = 1/2 Pp total) 6. From the sums of all the different kinds of offspring genotypes, create a genotypic fraction 1/4 PP, 1/2 Pp, 1/4 pp is in the ratio 1 PP : 2 Pp : 1 pp 7.Based on dominant and recessive rules, determine the phenotypic fraction A genotypic ratio of 1 PP : 2 Pp : 1 pp yields 3 purple-flowered plants : 1 white-flowered plant |
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A test cross
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is used to deduce whether an organism with a dominant phenotype is homozygous or heterozygous
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the test cross process
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Cross the unknown dominant-phenotype organism (P_) with a homozygous recessive organism (pp)
If the dominant-phenotype organism is homozygous dominant (PP), only dominant-phenotype offspring will be produced (Pp) If the dominant-phenotype organism is heterozygous (Pp), approximately half the offspring will be of recessive phenotype (pp) |
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How is sex determined in the offspring?
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Mammals have a set of sex chromosomes that dictate gender
Females have two X chromosomes Males have an X chromosome and a Y chromosome The rest of the (non-sex) chromosomes occur in identical pairs and are called autosomes For organisms in which males are XY and females are XX, the sex chromosome carried by the sperm determines the sex of the offspring During sperm formation, each sperm receives either the X or the Y chromosome, along with a copy of each of the autosomes Because the female has only X sex chromosomes, the unfertilized egg will always have just an X chromosome If the egg is fertilized by a sperm with a Y chromosome, a male results; if fertilized by an X-bearing sperm, a female is produced |
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Many traits do not follow simple Mendelian rules of inheritance
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Not all traits are completely controlled by a single gene
A trait may not be completely dominant to another |
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Incomplete dominance
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In the genes studied by Mendel, one allele was dominant over the other, which was recessive
Some alleles, however, are incompletely dominant over others When the heterozygous phenotype is intermediate between the two homozygous phenotypes, the pattern of inheritance is called incomplete dominance |
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When the heterozygous phenotype is intermediate between the two homozygous phenotypes, the pattern of inheritance is called
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incomplete dominance
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An individual may have at most how many alleles?
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two
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A species may have multiple alleles for a given characteristic
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However, each individual still carries two alleles for this characteristic
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When heterozygotes express the phenotypes of both of the homozygotes (in this case, both A and B glycoproteins), the pattern of inheritance is called
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codominance
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People make antibodies to the type of glycoproteins they
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lack
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The incorrect separation of chromosomes in meiosis is known as
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as nondisjunction
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Nondisjunction causes gametes to have
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too many and too few chromosomes
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Some genetic disorders are caused by abnormal
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numbers of autosomes
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In trisomy 21 (Down syndrome)
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afflicted individuals have three copies of chromosome 21
Down syndrome includes several distinctive physical characteristics, including weak muscle tone, a small mouth held partially open because it cannot accommodate the tongue, and distinctively shaped eyelids Down syndrome is also characterized by low resistance to infectious diseases, heart malformations, and varying degrees of mental retardation, often severe |
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The environment influences the expression of genes
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The environment in which an organism lives profoundly affects its phenotype
Newborn Siamese cats demonstrate the effect of environment on phenotype A Siamese cat has the genotype for dark fur all over its body However, the enzyme that produces the dark pigment is inactive at temperatures above 93°F (34°C) When kittens are in the all-encompassing warmth of their mother’s uterus, the enzyme is inactive and they are born with pale fur everywhere on their bodies After birth, the ears, nose, paws, and tail become cooler than the rest of the body, and dark pigment is produced there in the pattern characteristic of the breed |
