Term
| Viruses are classified according to what 3 criteria? |
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Definition
Host organism
Nature of genetic material
Reproductive cycle |
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Term
| Viruses are obligate parasites and thus lack: |
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Definition
| nucleotides, enzymes, and protein synthesis capabilities |
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Term
| Lytic virus that infects E. coli |
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Definition
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Term
| What are the 3 sets of genes present in viral genomes? |
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Definition
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Term
| Define "vegetative phage." |
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Definition
| Viral DNA that has been inserted into the host cell |
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Term
| Phage T4 and plasmids duplicate their DNA in what manner? |
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Definition
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Term
| What is the purpose of early viral genes? |
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Definition
| produce proteins to inhibit host transcription and protein synthesis |
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Term
| What is the purpose of DNA metabolism genes? |
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Definition
| to produce nucleases and replication proteins |
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Term
| What is the purpose of the late viral genes? |
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Definition
| to produce lysozymes and rupture the cell membrane |
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Term
| What are the dimensions of the Phage T4? |
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Definition
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Term
| This virus infects E. coli cells and can enter into either a lytic or lysogenic cycle. |
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Definition
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Term
| Lysogenic viruses produce a ___________ that inhibits the expression of lytic genes. |
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Definition
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Term
| Define "vegetative chromosome." |
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Definition
| viral chromosome is free in the cytoplasm of the cell |
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Term
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Definition
| viral DNA that has been integrated into the host genome (provirus in higher organisms) |
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Term
| Which genes of the E. coli and Phage lambda genome pair up and cross over? |
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Definition
| ATTcoli and ATTlambda genes |
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Term
| Induction can be stimulated by: |
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Definition
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Term
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Definition
| lytic cycle is induced by UV light or chemicals |
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Term
| Lysogenic viruses spontaneously become lytic in one out of ____________ cell divisions. |
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Definition
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Term
| ____________ contain RNA as genetic material. |
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Definition
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Term
| Mapping viral chromosomes is achieved with what kind of infections? |
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Definition
| lytic, multiple, mixed infections. |
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Term
| What does the h gene in Phage T4 do? |
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Definition
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Term
| What does the r gene of Phage T4 do? |
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Definition
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Term
| An h+r+ virus in E. coli will appear as: |
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Definition
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Term
| Describe the process of mapping viral chromosomes. |
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Definition
1. a. infect E. coli cells with T4h+r+ and T4hr.
1. b. r+ will appear as small, turbid plaques in the bacteria, while r will form large, clear plaques.
2. Recover recombinants |
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Term
| Bacterial recombination can occur in three ways. Name them. |
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Definition
1. Conjugation
2. Transformation
3. Transduction |
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Term
| Conjugation was first studied by whom? |
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Definition
| Lederberg and Tatum (1946) |
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Term
| E. coli K12 strain Y-10 requires which nutrients? |
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Definition
| threonine, lysine, and thiamine |
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Term
| E. coli K12 strain Y-24 requires which nutrients? |
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Definition
| phenylalanine, cysteine, and biotin |
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Term
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Definition
| random switch of a recessive allele to the wild type |
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Term
| Describe Lederberg and Tatum's experiment. |
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Definition
Crossed Y-10 and Y-24 strains of E. coli K12 and observed a higher frequency of recombination than could be attributed to back mutation
CONJUGATION |
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Term
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Definition
| "fertility factor;" codes for production of F pili (conjugation tube) |
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Term
| Active F+ cells are called __________ cells. |
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Definition
| Hfr (high frequency recombination) |
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Term
| T or F: F factor is in a separate plasmid, so it does not recombine. |
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Definition
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Term
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Definition
| partial zygotes resulting from the interruption of conjugation that are still able to recombine, but do not become F+ due to incomplete transfer of F genes |
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Term
| An F+ cell in which the F plasmid was incorporated into the main chromosome is called ___________. |
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Definition
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Term
| Describe Jacob and Wollman's first experiment. |
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Definition
1. Mixed HFR-H and F- cells for 60 minutes (not long enough for complete recombination)
2. Plated cells on minimal media with streptomycin to select for thr+leu+strR cells (linked genes)
3. Plated recombinants on minimal media with:
sodium azide, PhageT1, lactose or galactose.
4. Results: Percentage of recombinants reflected relative location of genes |
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Term
| Describe Jacob and Wollman's second experiment. |
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Definition
1. Mixed Hfr-H and F- cells in a blender to interrupt conjugation at specific times.
2. Started blender after a certain period of time and determined the recombinants.
Results: Thr transferred 1st based on time; str last as none showed recombination. Thus thr first on F plasmid and str last. |
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Term
| How does the chromosome map of Hfr-4 compare to that of Hfr-H? |
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Definition
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Term
| Transformation was first studied by whom? |
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Definition
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Term
| Describe Griffith's experiment. |
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Definition
1. Injected mice with various strains of streptococcus pneumoniae.
a. SIII - died
b. RII - didn't die
c. heat killed SIII - didn't die
d. RII & hk SIII - died; live SIII recovered from blood.
TRANSFORMING PRINCIPLE |
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Term
| Describe Avery, MacLeod and McCarty's experiment. |
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Definition
| Fractionated s. pneumoniae type S and mixed each component with living R bacteria. Only DNA caused R->S transformation; therefore, DNA is the genetic material. |
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Term
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Definition
| one strain of bacteria takes up free DNA from a lysed bacteria |
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Term
| Describe Hotchkiss and Marmur's experiments. |
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Definition
Host cells contained mtl-str(s) genes while two donors (one mtl+ and the other str(r)) were added. When a single donor (mtl+str(s)) was used, the rate of transformation increased. Additionally, the two genes are close enough on the chromosome that cotransformation is likely.
Cotransformation can be used to measure the distance between genes. |
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Term
| Describe Zinder and Lederger's experiment. |
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Definition
Separated two strains of bacteria with a glass filter. Strain A harbored lytic Phage P22 while Strain B was lysogenic. Recombinants were recovered.
Cotransduction possible. |
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Term
| Define 'transducing particle.' |
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Definition
| host DNA incorporated into phage coat and inserted into another bacterium |
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Term
| When mapping the relative locations of genes in E. coli chromosomes, one should study _________. |
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Definition
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Term
| When mapping the fine structure of genes in E. coli chromosomes, one should study _____________. |
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Definition
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Term
| A lysogenic virus of E. coli K12 is called _______________. |
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Definition
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Term
| Describe Lederberg's specialized transduction experiment. |
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Definition
1. A gal+ culture of E. coli was inoculated with phage lambda.
2. Radiated w/ UV light to induce lysis
3. Lysate used to infect gal- culture
4. small number of recombinants w/ gal+ also retained gal- gene
lambdadgal in lysate defective for part of phage genome and contained gal+ genes from E. coli |
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Term
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Definition
| defective viral chromosome lacking some viral genes and containing the gal+ gene cluster |
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Term
| True or False: RNA polymerase adds ribonucleotides to the 3' end. |
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Definition
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Term
| Name four ways in which transcription differs from replication. |
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Definition
1. ribonucleotides
2. uracil replaces thymine
3. sstemplate
4. localized (small sections) |
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