A cross is made between the following two E. coli strains: Hfr arg leu bio x F a
ID: 322464 • Letter: A
Question
A cross is made between the following two E. coli strains: Hfr arg leu bio x F arg leu bio Interrupted mating studies show that arg enters the recipient cell last, so arg recombinants are selected on minimal medium that is supplemented with biotin and leucine only (no arginine). These recombinants are then tested for the presence of leu and bio. The following numbers of individuals are found for each genotype: What is the gene order for these three genes? What are the map distances between the genes in recombination percentages? DNA from a bacterial strain that is his leu lac is used to transform a strain that is his leu lac. The following percentages of cells are transformed:Explanation / Answer
a. Determination of gene order by comparing arg + bio + leu - with arg + bio - leu +, if the order were arg leu bio
b. Recombination frequency (RF) : crossing over event between arg and bio genes100% (72) / 500 = 14.4 % (m.u)
similarly cross over event between bio -leu distance is estimated by arg+ bio+ leu- colony type
RF : 100% 22 / 500 = 4.4 % (m.u)
2. DNA from a bacterial strain that is his + leu+ lac+ is used transform a strain that his - leu- lac- the following percentage of cells transformed
Donor strain receipent strain genotype of transformed cells percentages:
his+leu+lac+his-leuc-lac-his+leu+lac+0.02
his+leu+lac- 0.00
his+leu-lac+ 2.00
his+leu-lac- 4.00
his-leu+lac+ 0.10
his-leu-lac+ 3.00
his-leu+lac- 1.50
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