Question

In flower beetles, pygmy (py) is recessive to normal size (py+), and red color (r) is recessive to brown (r+). A beetle heterozygous for these characteristics was test-crossed to a beetle homozygous for pygmy and red. The following are progeny phenotypes from this testcross.

py+ r+ 178
py+ r 21
py r+ 19
py r 182
Total 400
What is the map distance between the py and r loci.

Answer 1

The map distance between the py and r loci is 10 map units.

Step-by-step explanation:

To determine the map distance between the py and r loci, we need to calculate the recombination frequency. The recombination frequency is determined by the formula:

Recombination frequency = (Recombinant progeny / Total progeny) * 100

In this case, the recombinant progeny consists of the py r+ and py+ r offspring, which add up to 21 + 19 = 40. The total progeny is 400. Therefore, the recombination frequency is (40 / 400) * 100 = 10%.

Since 1% recombination frequency corresponds to 1 map unit, the map distance between the py and r loci in this case is 10 map units.