The Genetics Of Bacteria And Their Viruses - Introduction to Genetic Analysis

Bernard Davis tested the "cross-feeding" interpretation of some data that showed the phenotype of one microbe as capable of being changed by another microbe.His contribution can be summarized as:

A)using one strain of microbes as food for another,and then evaluating the impact upon microbial phenotype.
B)combining microbes with complementing auxotrophs in a single tube and then analyzing the cells of gene exchange.
C)placing a barrier between bacterial strains with complementing auxotrophs to assess whether contact between cells was required for genetic exchange.
D)using fungi to feed bacterial strains with unusual auxotrophic mutations.
E)Davis was not a significant contributor to this research question.

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Question 2

(Multiple Choice)

Free

An F⁺ microbial strain would best be described as:

A)any bacterium that readily takes up naked DNA through its membrane.
B)incapable of conjugation due to inhibitory genes on the F plasmid.
C)a bacterial strain with specific auxotrophic characteristics.
D)a bacterial strain that carries a phage with membrane fusion competency.
E)a bacterium with a plasmid that confers mating competency (or fertility).

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Question 3

(Multiple Choice)

Free

A cross is made between an Hfr strain that is Str^Sa⁺b⁺d⁺ in genotype and an F^- strain that is Str^Ra^-b^-d^- in genotype.Interrupted-mating studies show that b⁺ enters the recipient strain last,and that the Str locus is very far away from b⁺,so it never enters the recipient strain.The b⁺ recombinants are then tested for the presence of the a⁺ and d⁺ alleles.The following data were obtained:

\begin{array} { l l l l } a ^ { + } & b ^ { + } & d ^ { + } & 326 \\a^ { -} & b ^ { + } & d ^ { + } & 2 \\a ^ { + } & b ^ { + } & d^ { -} & 14 \\a ^ { -}& b ^ { + } & d ^ { -}& \underline { 58 } \\& && 400\end{array}

a)What is the gene order?

A)a d b Str
B)b a d Str
C)b d a Str
D)d a b Str
E)d b a Str

Answer