Understanding recombination in bacteria and in viruses that infect bacteria.

A cross is made between Hfr met+ thi+ pur+ X F- met- thi- pur-. Interrupted-mating studies show that met+ enters the recipient last, so met+ exconjugants are selected on medium containing thi and pur only. These exconjugants are tested for the presence of thi+ and pur+. The following numbers of individuals are found with each genotype: met+ thi+ pur+ 280 met+ thi+ pur- 0 met+ thi- pur+ 6 met+ thi- pur- 52 (a) Why was met left out of the selection medium? (b) What is the gene order? (c) What are the map distances in recombination units?

The definitions of merozygote, recombinant frequency, recessive phenotype and sex chromosome.

Define the following terms: MEROZYGOTE RECOMBINANT FREQUENCY (RF) RECESSIVE PHENOTYPE SEX CHROMOSOME

The definition of a transposable genetic element.

Define transposable genetic element.

Recombination in bacteria is defined.

A particular Hfr strain normally transmits the pro+ marker as the last one during conjugation. In a cross of this strain with an F- strain, some pro+ recombinants are recovered early in the mating process. When these pro+ cells are mixed with F- cells, the majority of the latter are converted to pro+ cells that also carry the F factor. This job furthger explains these results.

Understanding recombination in bacteria.

A transformation experiment is performed with a donor strain that is resistant to four drugs: A, B, C, D. The recipient is sensitive to all four drugs. The treated recipient-cell population is divided up and plated on media containing various combinations of the drugs. The results are shown in the table below. Drug # colonies NONE 10000 A 1156 B 1148 C 1161 D 1139 AB 46 AC 640 AD 942 BC 51 BD 49 CD 786 ABC 30 ABD 42 ACD 630 BCD 36 ABCD 30 (a) One of the genes obviously is quite distant from the other three, which appear ... click for more