Midterm #3
Midterm #3 1. A single, visible isolated colony of bacteria growing on an agar plate represents: a. Approx. 100 bacterial cells b. A population of auxotrophic bacteria, since prototrophic bacteria can’t be grown on an agar plate. c. A mixture of several variants, die to differences in DNA sequence, but which all belong to the same species d. A population of bacteria derived by multiple cell divisions starting from a single cell. e. None of the above 2. During the phage lytic cycle, which one of the following events would not occur? a. Integration of the phage genome into the bacterial genome b. Lysis of the bacterial cell to release new phage progeny c. Fragmentation of the bacterial cell’s chromosomal DNA d. Synthesis of phage proteins 3. An E. Coli cell has the following genotype: bio- leu- arg- It is trasnfermed with DNA from a strain that is bio+leu+arg+. Which of the following genomic arrangements is consitant with these reults? 1 Arg+ 19% bio+ 8% leu+ 2 Leu+ 3% bio+ 7 % arg+ a. Bio arg leu b. Arg bio leu c. Arg bio leu d. Bio leu arg 4. IN E. Coli DnaA protein: a. Is the helicase used to separate the template strands during replication b. Coats the newly synthesized DNA strands at the replication fork to prevent them from base-pairing c. Binds conserved sequence box elements located at the chromoal origin of DNA replciaiton d. Removes supercoilds from the DNA e. Synthesizes the leading strand during DNA replcaition 5. The Herhsey-Chase experiment was an mportant experiement that demonstrated that DNA was heritable marterial. The researchers used a virus that had either its DNA or protein componenets specifically radioactively labeled. Which one fo the following statements aout this experiment is false. a. Researchers used a bacteriophage to infect E Coli cells
6.
7.
8.
9.
b. The 32P labeled viral DNA did not enter the E. Coli cells and therefore researchers concluded that DNA was the heritable material. c. The 35S labeled viral proteins did not enter the E Coli cells and therefore researchers concluded that protein was not the heritable material entered the E coli cells d. Both types of radioactivity entered the E Coli cells but slightly more radioactively-labelled DNA was found inside the cells Which of the following correctly describes Chargaff’s base pairing rules? a. % (A+G) = % (c+ T) b. Different organisms always have 25% guanine c. Different organisms always have 25% thymine d. % adenine = % cytosine e. % (A+T) = % (G+C) R plasmids spread antibiotic resistant genes rapidly through bacterial populations because: a. Recombination with the chromosome is not required to maintain antibiotic resistance genes in recipient cells following cognation b. Recombination with the chromosome occurs with much higher frequency in recipient cells following conjugation c. Conjugation is not required to transfer R plasmids to recipient cells d. Donor cells containing R plasmids often undergo conjugation more often the F+ cells e. None of the above explains the reason for rapid spread of antibiotic resistance Which of the following correctly describes how the yeast proteins Cdc6 and Cdt1 regulate the timing of the start of DNA synthesis? a. They control the binding of the origin replciatoin complex (ORC) to an AT rich region specifically during S phase b. They inhibit the activity of the helicase required for tpleate DNA strand separation until the start of the S phase c. They control enzymatic activity of the yest DNA polymerase complexes d. They only allow the helicase to bind to the origin of replication at the start of the S phase e. They get degraded during G1 phsae of the cell cycle When the F- cell receives chromosomal DNA from an HFR strain, recombination must occur through an evn number of crossover events because: a. The transferred DNA is double-stranded b. The transferred DNA is linear c. The f- Cell’s chromosome must remain linear d. The exogenote DNA will be degraded e. The Endogenote DNA will be degraded
10. Which od the following correctly describes the replcaition of eukaryotic chromosome such as a Drosophilia chromosome a. Replciation begins at one unique site on the chromosome b. Initiation of a new round of replciaiton beings before the previous round is complete c. There are many replicons on the chrosmome d. Each replcisome replciaies one half of the chromosome because replciaiton if bi-directional e. Lagging strand synthiss is much slower then leading strand 11. An auxotrophic E coli strain has the genotype ade+trp-met+ arg-. If we wish to successfully isolate E. Coli cells thata are revertants for the trp allele, that is trp+ cells, we should grow the E. coli cells in agar plates supplemented with: a. Nothig b. Trp c. Trp, ade, met d. Arg e. Trp and Arg 12. Which of the following statements about deoxynucleotide structure is correct? a. The nitrogenous base is attached to the C1 position b. There is at elase one phosphate groupe attached to the nitrogenous bse c. The sugar has a 2’ OH group d. The nitrogenous base can be adenine, guanine, cytosine or uracil e. None are correct. 13. Define the following terms a. Replicon (during DNA replciaiton)
b. F’ Plasmid
Answers: 1. D 2. A 3. A 4. C 5.B 6.A 7.A 8.B 9.C 11.D 12.A
6.
7.
8.
9.
b. The 32P labeled viral DNA did not enter the E. Coli cells and therefore researchers concluded that DNA was the heritable material. c. The 35S labeled viral proteins did not enter the E Coli cells and therefore researchers concluded that protein was not the heritable material entered the E coli cells d. Both types of radioactivity entered the E Coli cells but slightly more radioactively-labelled DNA was found inside the cells Which of the following correctly describes Chargaff’s base pairing rules? a. % (A+G) = % (c+ T) b. Different organisms always have 25% guanine c. Different organisms always have 25% thymine d. % adenine = % cytosine e. % (A+T) = % (G+C) R plasmids spread antibiotic resistant genes rapidly through bacterial populations because: a. Recombination with the chromosome is not required to maintain antibiotic resistance genes in recipient cells following cognation b. Recombination with the chromosome occurs with much higher frequency in recipient cells following conjugation c. Conjugation is not required to transfer R plasmids to recipient cells d. Donor cells containing R plasmids often undergo conjugation more often the F+ cells e. None of the above explains the reason for rapid spread of antibiotic resistance Which of the following correctly describes how the yeast proteins Cdc6 and Cdt1 regulate the timing of the start of DNA synthesis? a. They control the binding of the origin replciatoin complex (ORC) to an AT rich region specifically during S phase b. They inhibit the activity of the helicase required for tpleate DNA strand separation until the start of the S phase c. They control enzymatic activity of the yest DNA polymerase complexes d. They only allow the helicase to bind to the origin of replication at the start of the S phase e. They get degraded during G1 phsae of the cell cycle When the F- cell receives chromosomal DNA from an HFR strain, recombination must occur through an evn number of crossover events because: a. The transferred DNA is double-stranded b. The transferred DNA is linear c. The f- Cell’s chromosome must remain linear d. The exogenote DNA will be degraded e. The Endogenote DNA will be degraded
10. Which od the following correctly describes the replcaition of eukaryotic chromosome such as a Drosophilia chromosome a. Replciation begins at one unique site on the chromosome b. Initiation of a new round of replciaiton beings before the previous round is complete c. There are many replicons on the chrosmome d. Each replcisome replciaies one half of the chromosome because replciaiton if bi-directional e. Lagging strand synthiss is much slower then leading strand 11. An auxotrophic E coli strain has the genotype ade+trp-met+ arg-. If we wish to successfully isolate E. Coli cells thata are revertants for the trp allele, that is trp+ cells, we should grow the E. coli cells in agar plates supplemented with: a. Nothig b. Trp c. Trp, ade, met d. Arg e. Trp and Arg 12. Which of the following statements about deoxynucleotide structure is correct? a. The nitrogenous base is attached to the C1 position b. There is at elase one phosphate groupe attached to the nitrogenous bse c. The sugar has a 2’ OH group d. The nitrogenous base can be adenine, guanine, cytosine or uracil e. None are correct. 13. Define the following terms a. Replicon (during DNA replciaiton)
b. F’ Plasmid
Answers: 1. D 2. A 3. A 4. C 5.B 6.A 7.A 8.B 9.C 11.D 12.A
