Question

Researchers studied the linkage of three genes affecting kidney function in mice: cyp, ren, and tu. They carried out a series of three point testcrosses, mating mice that were heterozygous at all three loci with mice that were homozygous for the recessive alleles at all three loci. The following table lists the results of the testcrosses. Plusses represent dominant wild-type alleles. Phenotype Number ren 310 сур + 320 сур ren tu 90 + + 55 + ren lu 30 сур + + 45 сур ren + 3 total 857 a. Determine the order of the loci that encode cyp, ren, and tu on the chromosome, the map distances between them, and the interference and coefficient of coincidence for these genes. b. Draw a picture of the two chromosomes in the triple heterozygous mice used in the testcrosses, indicating which of the alleles are present on each chromosome.

please answer both questions.

Answer 1

Formulas for three point test cross -

?# total types of progenies = 8

?Parental progenies = 2 = maximum in #

?Double cross over progenies (DCO) = 2 = minimum in #

?Single cross over progenies (SCO) = 4 = intermediate in #

?Distance between two genes = (SCO between those two genes + DCO) × 100 / total # progenies

?Recombination frequency = gene distance / 100

?Expected DCO = recombination frequency between first two genes × recombination frequency between next two genes × 100

?Observed DCO = number of DCO / total # progenies × 100

?Coefficient of coincidence = observed DCO / expected DCO

?Interference = 1 - coefficient of coincidence

Solution -

DCO cup Parental A puogeneis = trent cupt rent tt tu t tu Men 90 up ir middle. cup dist. b/w run- upp: Man tt een cypte t tt • Cyptu 90+55+3+4 100 857 55 7 17-73 mu 9.56 mu 100 - dist. b/w cup- tu = 30x45+3+4 857 0.81.1 S obs DCO = 100 344 857 1.69.7: 100 exp DCO= 17.73 9.56 100 100 0.48 Coc= 0.6L 1.69 0.52 I= 1-0.48 B cup a tu cup + 07 Of

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