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67 Cards in this Set
- Front
- Back
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Genetics |
- the science of heredity, includes study of genes; how they carry information, how they replicate and pass to subsequent generations of cells or between organisms. |
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genome |
- the genetic information in the cell
- a cell's genome includes Chromosomes and Plasmids |
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Chromosomes |
- structures containing DNA that physically carry hereditary information, contain genes. - A bacterium has a single circular choromosome consisting of a single circular molecule of DNA |
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Current Definition of GENE |
are segments of DNA (except in some viruses, in which they are made of RNA) that code for functional products -could be several thousand or more base pairs long |
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DNA base pairs |
- pair of nitrogenous bases on seperate strands that hold the two strands together by hydrogen bonds Adenine/Thymine Cytosine/Guanine |
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Nucleotide |
structural units of nucleic acids made up of: 1. 5-carbon sugar (ribose in RNA, deoxy in DNA) 2. a phosphate 3. a nitrogenous base; either a purine or pyrimidine |
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Genetic Code |
- is the universal set of rules that determine how a nucleotide sequence is converted into an amino acid sequence |
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Genotype vs. Phenotype |
Genotype: genetic makeup, potential properties, but not the properties themselves Phenotype: actual, expressed properties. The manifestation of a genotype. |
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Short Tandem Repeats (STRs) |
- noncoding regions composed of repeating sequences of two to five-base sequences. These are used in DNA fingerprinting, |
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Genomics |
the sequencing and molecular characterization of genomes |
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Codon |
- groups of three nucleotides, such as AUG, that makes up the language of mRNA. - the sequence of codons on an mRNA molecule determines the sequence of amino acids that will be in the protein being synthesized. Each codon codes for a particular amino acid. |
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Transcription |
synthesis of a complementary strand of RNA from a DNA template |
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mRNA |
carries the genetic code for a protein out from the chromosome to ribosomes |
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tRNA |
carries individual amino acids to the messenger RNA which puts them in proper sequence |
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rRNA |
links up the amino acids to form a protein - forms an integral part of the ribosomes |
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Translation |
RNA making a protein, the use of mRNA as a template in the synthesis of a protein 1. Components needed to begin translation come together. 2. On the assembled ribosome, a rRNA carrying the first amino acid is paired with the start codon on the mRNA. The place where this first tRNA sits is called the P site. A tRNA carrying the second amino acid approaches. 3. The second codon of the mRNA pairs with a tRNA carrying the second amino acid at the A site. The first amino acid joins to the second by a peptide bond. This attaches the polypeptide to the tRNA in the P site. 4. The ribosome moves along the tmRNA until the second tRNA is in the P site. The next codon to be translated is brought into the A site. THe first tRNA now occupies the E site. 5. The second amino acid joins to the third by another peptide bond, and the first tRNA is released from the E site. 6. The ribosome continues to move along the mRNA, and new amino acids are added to the polypeptide. 7. When the ribosome reaches a stop codon, the polypeptide is released. 8. Finally, the last tRNA is released and the robosome come apart. The released polypeptide forms a new protein. |
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genetic recombination |
the process of joining pieces of DNA from different sources - usually involves DNA from different organisms - contributes to genetic diversity |
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transformation |
the process in which genes are transferred from one bacterium to another as "naked" DNA in solution |
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transduction |
the transfer of DNA from one cell to another by a bacteriophage - in generalized transduction, any bacterial genes can be transferred |
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bacteriocins |
- toxic proteins that kill other bacteria - these may be contained in plasmids, useful makers for identification of certain bacteria |
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Resistance Factors (R factors) |
a bacterial plasmid carrrying genes that determine resistance to antibiotics - contain 2 groups of genes 1. resistance transfer factor (RTF): genes for plasmid replication and conjugation 2. resistance genes (production of enzymes that inactive drugs) |
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Why are R factors important in the treatment of infectious diseases? |
- R factors lets us know which treatment will be most effective for an infectious disease |
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Transposons (rare) |
- a small piece of DNA that can move from one DNA molecule to another - frequent movement of transposons = havoc in cell - insertion within genes may inactivate them - may be spread between organisms since they may be carried between cells on plasmids or viruses |
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Describe how DNA serves as genetic information (refer to Chp. 2, figure 2.16 as needed) |
- DNA is a double-stranded molecule that stores genetic information - alternating sugar and phosphate groups form the backbone of the double helix - rungs formed by nitrogen-containin bases |
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DNA nucleotide |
deoxyribonucleic acid 1. Pentose Sugar = Deoxyribose 2. Phosphate Group 3. Nitrogenous Base = A, T, C, G |
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RNA nucleotide |
ribonucleic acid 1. Pentose Sugar = Ribose 2. Phosphate Group 3. Nitrogenous Bases = A, U, C, G |
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Draw one nucleotide |
lolkay |
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Compare and contrast a portion of a DNA vs. RNA molecule (see table 2.6) |
DNA: Composition: sugar = deoxyribose Nitrogen containing bases: C, G, A, T Function: Determines all hereditary traits |
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Compare and contrast a portion of a DNA vs. RNA molecule (see table 2.6)
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RNA: Strands: Single-stranded in cells and most RNA viruses; Double-stranded in some viruses (reoviruses) Composition: sugar = ribose Nitrogen containing bases are C, G, A, U Function: Protein sythesis |
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Describe the process of DNA replication (include in your description: semiconservative, replication fork, DNA gyrase, DNA ligase, and DNA polymerase) |
1. Supercoiling of DNA is relaxed by topoisomerase or gyrase 2. Two strands of parental DNA are unwound by helicase and seperated from each other in one small DNA segment after another 3. Free nucleotides present in the cell cytoplasm are matched up to the exposed bases of the single-stranded parental DNA - bases must be complimentary (thymine with adenine) 4. Any bases improperly base paired are removed and replaced by replication enzymes 5. Newly added nuceotide joined to growing DNA strand by DNA polymerase 6. Parental DNA is unwound a bit further to allow addition of more nucleotides, called the replication fork 7. replication is semiconservative because each new DNA molecule contains one original strand and one new strand 8. DNA ligase joines the discontinuous fragments of the lagging strand |
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DNA Gyrase |
relaxes the supercoiling ahead of replication fork |
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DNA Ligase |
makes covalent bonds to join the DNA strands; Okazaki fragments and new segments in excision repair |
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DNA polymerases |
sythesizes DNA, proofreads and repairs DNA |
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Transcription in Prokaryotic Cells |
1. RNA polymerase binds to the promoter, and DNA unwinds at the beginning of a gene. 2. RNA is synthesized by complementary base pairing of free nucleotides with the nucleotide bases on the template strand of DNA. 3. The site synthesis moves along DNA; DNA that has been transcribed rewinds. 4. Transcription reaches the terminator. 5. RNA and RNA polymerase are released, and the DNA helix-reforms. |
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Transcription in Eukaryotic Cells |
Takes place in nucleus. mRNA must be completely synthesized and moved through the nucleur membrane to the cytoplasm before translation can begin. In addition, the RNA undergoes processsing before it can leave the nucleus. |
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Eukaryotic Genes: Exons |
regions of DNA expressed |
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Eukaryotic Genes: Introns |
intervening regions of DNA that do not code for a protein |
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Explain the relationship between genes and proteins |
Genes = units of biological information encoded by sequence of nucleotide bases in DNA. |
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Operon |
- the operator and promoter sites and structural genes they control Inducible operon: ie. repressor binds to the operator site preventing transcription. In presence of lactose, the repressor binds with a metabolite of lactose which allows lactose-digesting enzymes to be transcribed In repressible operons: structural genes transcribed until they are turned off |
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Pre-Transcriptional Regulation |
- control the formation and amounts of enzymes in the cell Repression: inhibits gene expression and decreases synthesis of enzymes (by repressors) Induction: turns on transcription of a gene or genes (by an inducer) |
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Post-Transcriptional Regulation |
microRNAs (miRNAs) inhibit protein production in eukaryotic cells |
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mutation |
a change in the nitrogenous base sequence of DNA - may sometimes cause a change in the product encoded by that gene |
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Silent (Neutral) |
- change in DNA base sequences causes no change in activity of product encoded by that gene |
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Base Substitution (Point Mutation) |
single base at one point in the DNA sequence is replaced with a different base
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Missense Mutation |
a base substitution that results in an amino acid substitution in the synthesized protein
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Nonsense Mutation |
base substitution resulting in a nonsense codon
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Frameshift Mutation |
or or a few nucleotide pairs are deleted or inserted in DNA - causes changes in amino acids downstream from original mutation, most likely results in inactive protein |
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Spontaneous Mutations |
a mutation that occurs without a mutagen
- may be beneficial |
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mutagen |
an agent in the environment that brings about mutations -ie. certain chemicals and radiation |
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How can a mutation be beneficial? |
ie. a mutation that cofers antibiotic resistance is beneficial to a population of bacteria that is regularly exposed to antibiotics |
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How do mutagens affect the mutation rate? |
a mutagen usually increases the spontaneous rate of mutation (by a factor of 10 - 1000 times) |
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Why do we see mutant bacteria more often than mutant animals? |
- bacteria generally have only one copy of each gene per cell (effects of mutated gene are not masked by presence of a normal version of the gene, as in many eukaryotic animals) - bacteria also reproduce a lot faster than animals and increase chances of mutation - bacteria are able to transfer genetic information horizontally and vertically, while animals can only do so vertically |
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Ames Test |
- uses bacteria as carcinogen indicators This is done by comparing the number of histidine-synthesizing revertants between a control plate and an experimental plate. - routinely used to evaluate new chemicals and air and water pollutants |
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Horizontal Gene Transfer |
transfer of genetic information between cells of the same generation
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Vertical Gene Transfer |
transfer of genetic information to the next generation of cells - parent cell to daughter cells |
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Mechanisms of Genetic Recombination in Bacteria |
1. Transduction 2. Transformation 3. Conjugation |
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Why did encapsulated bacteria kill the mouse while nonencapsulated bacteria did not? |
The encapsulated bacteria killed the mouse because it was able to avoid phagocytosis. The nonencapsulated bacteria were readily destroyed by phagocytic defenses of the host. |
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What killed the mouse in (d)? |
This is due to transformation. The live nonencapsulated bacteria were transformed by the dead encapsulated bacteria so that they acquired the ability to form capsules and therefore cause disease. |
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anticodon |
a sequence of three bases that is complementary to a codon - in this way, a tRNA molecule can base-pair with its associated codon |
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sense codons |
code for amino acids |
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nonsense codons (stop codons) |
do not code for amino acids (signal end of protein's molecules) |
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conjugation |
the transfer of genetic material from one cell to another involving cell to cell contact - differs from transformation in that it: 1. requires cell-to-cell contact 2. conjugating cells must be generally be opposite mating type |
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Donor Cell |
a cell that carries a plasmid (F+ fertility factor) |
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Recipient Cell |
a cell that does not carry a plasmid (F-) |
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plasmids |
- small loops of extra chromosomal DNA in bacteria (self replicating) - often carry genes of virulence, bacteriocins or drug resistance -can recombine into new combinations -DNA in plasmids can be shared between organisms via conjugation pili |
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Describe how genetic mutation and recombination provide material for natural selection to act upon |
These processes provide diversity in the descendants of cells. Natural selection will act on diverse populations to ensure the survival of those fit for that particular environment. |
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Certain antibiotics such as streptomycin are known to bind to messenger RNA molecules. What effect would this have on the metabolism of a bacterium? |
the effect this would have on the metabolism of a bacterium is that the genetic information may be misread which may lead to improper proteins being made |
