Exam 6: Genetic Analysis and Mapping in Bacteria and Bacteriophage

What is the difference between F⁺ and F⁻ bacteria?

In a conjugation experiment,the Hfr donor is thr⁺,leu⁺,his⁺,str.The recipient is thr⁻,leu⁻,and his⁻ strˢ.Why would you use medium containing streptomycin to analyze your results?

Conjugation,transduction,and transformation all occur in nature.Which do you expect would more likely account for the acquisition of the genes for resistance to an antibiotic? Why? Which do you think would best account for the acquisition of genes from one bacterial species by another of a different genus? Why?

Which of the following allows the compilation of time-of-entry maps?

When F⁺ conjugation occurs successfully,only one copy of the F plasmid single-stranded DNA is transferred.What else must minimally occur?

In Hfr transfer,what happens to linear DNA that does not recombine with the host chromosome?

Jacob and colleagues developed a bacterial linkage map based on time.What kind of recombination was used?

When a soil bacterium infects a plant root and introduces its Ti plasmid,how does this affect both the infectious bacterium and the plant?

Which,if any,characteristics of bacterial gene transfer is/are useful in analyzing eukaryotic gene transfer?

Arabinose sugar is used by ara⁺ bacteria but cannot be used by ara⁻ mutants.When both ara3 and ara5 mutants are introduced into the same recipient via a vector,and the recipients still cannot use arabinose,what can you conclude?

In generalized transduction,a phage introduces a segment of donor DNA into the recipient cell.This is followed by recombination of the donor fragment with the recipient chromosome.Which of the following must occur?

In a partially diploid F′ exconjugant,there are two alleles for lac (1 and 2)and two alleles for his (3 and 4).The phenotype of this cell is identical to a lac 1 his 4 cell.What is the best interpretation?

Some bacteriophages can be either lytic or lysogenic.These are called ________ phages.

In a bacterial cross of an Hfr donor a⁺b⁺ with a recipient F⁻ a⁻b⁻,what would be a possible recombinant?

In five Hfr strains,each of which was used to build a time-of-entry map,the genes entered the recipient cells as follows: Strain 1: S L A C T F Strain 2: N P F T C A Strain 3: T F P N U Y Strain 4: S H Y U N P Strain 5: U N P F T C Which of the following represents a correct compilation of these results?

Refer to this text to answer the following questions. To map genes of a bacterial strain,conjugation must be interrupted at given times.Suppose you have Hfr cells of genotype a⁺ᵇ⁺ᶜ⁺ᵈ⁺ᵉ⁺ˢᵗʳᴿ and F⁼ cells of genotype a⁻ᵇ⁻ᶜ⁻ᵈ⁻ᵉ⁻ˢᵗʳˢ and you combine these two cultures in liquid medium in four blenders at time 0.After intervals of 3,6,9,and 12 minutes,you turn on successive blenders. -The resulting cultures were then plated on medium containing streptomycin.Why?

A large region of the F plasmid (~33 kb)is called the transfer region (tra)and contains about 40 genes necessary for conjugation.The gene traA codes for the protein pilin that is polymerized to form a pilus,using a number of other tra genes.The pilus is a hollow cylinder whose units disassemble once contact is made in order to "reel in" the recipient cell.What other functions of the tra genes are required for transfer?

Refer to this text to answer the following questions. To map genes of a bacterial strain,conjugation must be interrupted at given times.Suppose you have Hfr cells of genotype a⁺ᵇ⁺ᶜ⁺ᵈ⁺ᵉ⁺ˢᵗʳᴿ and F⁼ cells of genotype a⁻ᵇ⁻ᶜ⁻ᵈ⁻ᵉ⁻ˢᵗʳˢ and you combine these two cultures in liquid medium in four blenders at time 0.After intervals of 3,6,9,and 12 minutes,you turn on successive blenders. -What role does the blender play in the experiment?

This graph shows the results of plating the cultures of each blender.What is the correct order of the genes on this chromosome?

One kind of plasmid in bacteria is called an R plasmid.What kinds of genes are typical of such plasmids?