Where I am confused with this particular question is how exactly to even start a

Question

Where I am confused with this particular question is how exactly to even start and how to derive the answer, as well as why it works out that way.

Here's the question:
In corn, a triple heterozygote was obtained carrying the mutant alleles s (shrunken), w (white aleurone), and y (waxy endosperm), all paired with their normal wild-type alleles. This triple heterozygote was testcrossed, and the progeny contained 116 shrunken, white; 4 fully wild-type; 2538 shrunken; 601 shrunken, waxy; 626 white; 2708 white, waxy; 2 shrunken, white, waxy; and 113 waxy.

a) determine if any of these three loci are linked and, if so, show map distances.

b) show the allele arrangement on the chromosomes of the triple heterozygote used in the testcross.

Explanation / Answer

Given that in corn there are three mutant alleles They are s ( shrunken) w( white aleurone) y( waxy endosperm) Paired with normal wild-type alleles s+, w+, y+ After test cross the progeny are 116 shrunken, white; 4 fully wild-type; 2538 shrunken; 601 shrunken, waxy; 626 white; 2708 white, waxy; 2 shrunken, white, waxy; and 113 waxy. W y+ s = 116 s+ w+ y+ = 4 w+ y+ s = 2538 w+ y s = 601 s+ y+ w = 626 w y s+ = 2708 s w y = 2 s+ w+ y = 113 Total progeny are 6708 Recombinants between s and w = 2538 + 601+ 626+ 2708 = 6473 % of recombination = 6473 / 6708 = 0.964 Recombinants between w and y = 116+ 601+ 626+ 113 = 456 % of recombination = 456 / 6708 = 0.067 Recombinants between s and y = 116 + 2538+ 2708+ 113 = 5475 % of recombination = 5475 / 6708 = 0.816 a) So, all three loci are linked and the map distances are s-----------------------y-----------w . b) Allele arrangement on the chromosomes of the triple heterozygote used in the testcross is s+-------------------------y--------w+ s--------------------------y+-------w

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