In corn, the genes for the following three traits are linked on the same chromosome: plant color, yellow (y) is recessive to green (Y); endosperm shape, shrunken (sh) is recessive to non-shrunken (Sh); and seed color, colorless (c) is recessive to colored (C). A plant heterozygous for these three genes was testcrossed and the resultant progeny and the number of each are listed below (the alleles designate the phenotype):

Phenotype Number of progeny

y sh c 95

Y Sh C 100

y Sh C 3

Y sh c 2

y sh C 20

Y Sh c 25

y Sh c 375

Y sh C 380

-Determine the order of the genes on the chromosome.

-Calculate the map distance between the genes.

-Determine the coefficient of coincidence and interference.

-Draw the alleles found on the chromosomes of the homozygous parents and the heterozygous plant used in the testcross.

Question

Biology

Turner Sosa

24 September, 11:36

In corn, the genes for the following three traits are linked on the same chromosome: plant color, yellow (y) is recessive to green (Y); endosperm shape, shrunken (sh) is recessive to non-shrunken (Sh); and seed color, colorless (c) is recessive to colored (C). A plant heterozygous for these three genes was testcrossed and the resultant progeny and the number of each are listed below (the alleles designate the phenotype):

Phenotype Number of progeny

y sh c 95

Y Sh C 100

y Sh C 3

Y sh c 2

y sh C 20

Y Sh c 25

y Sh c 375

Y sh C 380

-Determine the order of the genes on the chromosome.

-Calculate the map distance between the genes.

-Determine the coefficient of coincidence and interference.

-Draw the alleles found on the chromosomes of the homozygous parents and the heterozygous plant used in the testcross.

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Answers (1)

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Alana Morton · Answer 1

As per previous submission, the map distance between Wx & V is 7 mu and Sh & V is 30 mu.

Coefficient of coincidence = No. of observed double cross overs / No. of Expected double cross overs

Expected double cross overs frequency = product of single cross over frequencies (map distance / 100 = frequency)

= 0.07 x 0.3 = 0.021

Number of expected double cross overs = 0.021 x Total progeny = 0.021 x 10,756 = 225.8

So Coefficient of coincidence = (87+94) / 225.8

= 0.8

Then Interference - 1 - Coefficient of coincidence = 1-0.8 = 0.2

answer is A