Exam 7: Bacterial and Viral Genetic Systems

A retrovirus has an RNA genome but integrates into the DNA chromosome of a host cell.Explain how it does this.

You are using phages to map three toxin-production genes (R, Y, andG)in a new bacterium.You grow phages in a strain of the bacteria that produces all three toxins (R⁺, Y⁺, G⁺), isolate the phage, and then infect a second bacterial strain that cannot produce any of the toxins (R^-, Y^-, G^-).The recipient bacteria are then grown on colorimetric media (media that change color in response to toxin presence)to see which toxin genes are transferred together by the phage.The data are as follows: a.What kind of mapping is this called? b.Which gene is in the middle? c.Which of the outside genes is closer to the middle gene?

What happens to the remainder of the donated chromosome after crossing over has taken place in the recipient cell?

Two different strains of a mutant phage infected a single bacterium.One phage strain is a^-b⁺ and the other is a⁺b^-.The coinfected phages produced the wild-type phenotype in the bacterium: progeny phages were diluted and plated on a bacterial lawn.The resulting plaques produced the following genotypes: 19 a⁺ b⁺, 31 a^-b⁺, 29 a⁺b^-, 21 a^-b^-.What is the recombination frequency between the a and b genes?

When the F factor episome integrates into the E.coli chromosome, the result is which of the following strains?

Which of the following statements about retroviruses is FALSE?

Two different strains of a mutant phage infect a single bacterium.One phage strain is d^- and the other is e^-.Some of the progeny phages are genotype d⁺e⁺, and some are d^-e^-.What genetic phenomenon does this demonstrate?

Both retroviruses and lysogenic bacteriophages employ a mechanism that allows them to be replicated and passed from cell to cell without producing viruses.What is the common mechanism that these two very different viruses use?

_____ medium contains all of the substances required by bacteria for growth and reproduction.

Which of the following statements about nutritional requirement and growth of bacteria is NOT true?

Integrated, inactive, phage DNA is called a:

Outline the steps involved in mapping bacterial genes by generalized transduction.

You perform interrupted conjugation using an a⁺b⁺c⁺d⁺l⁺m⁺n⁺o⁺ Hfr strain and an F^- strain that is a^-b^-c^-d^-l^-m^-n^-o^-.You observe the following genes transferred together in order from last to first. n⁺a⁺c⁺m⁺ o⁺m⁺c⁺a⁺n⁺ o⁺b⁺d⁺l⁺n⁺ What is the map order of the genes?

HIV has a high mutation rate.What causes this, and how might this be advantageous to the virus?

(a)What is an F' plasmid, and how is it formed? (b)Explain how an F'can be used to construct a bacterial strain that is partially diploid.(c)Explain how partial diploid strains can be used to assess interactions between different alleles (e.g., lac⁺ and lac^-).

Which of the following will have the LEAST influence on the efficiency of transformation in E.coli bacteria?

Which of the following statements about genetic exchange in bacteria is NOT true?

Conjugation between an F' cell and an F^- cell may produce partial diploids called _____.

Which of the following refers to a slender extension of the cell membrane used for bacterial conjugation?

A bacterium of genotype a⁺b⁺c⁺d⁺ is the donor in a cotransformation mapping.The recipient is a^-b^-c^-d^-.Data from the transformed cells are shown below.What is the order of the genes? a⁺ and b⁺ 2 A⁺ and c⁺ 0 A⁺ and d⁺ 5 B⁺ and c⁺ 5 B⁺ and d⁺ 0 C⁺ and d⁺ 0