In a transformation experiment DNA of a pq strain was used t

In a transformation experiment, DNA of a p⁺q⁺ strain was used to transform a recipient strain that is auxotrophic for these markers. The number of each class of transformants is shown below:

Class

Genotype

Number

1

p⁺q⁺

405

2

p⁺q^–

300

3

p^–q⁺

195

4

p^–q^-

680

What is the map distance between these two loci? (2 points)

Solution

Answer:

The parental combinations are p+q+ & p-q- = 405+680 = 1085

The recombinants are p+q- & p-q+ = 300 + 195 = 495

The recombination frequency(RF) = (recombinant progeny/total progeny)100

RF = (495/1580)100

RF = 31.33%

(%) RF = (map units) Distance between the genes (loci)

31.33% = 31.33 map units

So the distance between the two loci is 31.33 map units