Assume that three pairs of alleles are found in Drosophila x

Assume that three pairs of alleles are found in Drosophila: x+ and x-, y+ and y-, and z+ and z-. As shown by the symbols, each non-wild-type allele is recessive to its wild-type allele. A cross between female heterozygous at these three loci and wild-type males yields progeny having the following genotypes: x+ y+ z+ females 1010 x- y+ z- males 430 x+ y- z+ males 441 x- y- z- males 39 x+ y+ z- males 32 x+ y+ z+ males 30 x- y- z+ males 27 x+ y- z- male 1 x- y+ z+ male 0

A.)What is the recombinant frequency between x and y? Decimal answer only. (Note: there is no crossing over in Drosophila males)

B.)What is the recombinant frequency between x and z? Decimal answer only.

C.)What is the coefficient of coincidence? Decimal answer only.

Solution

.)What is the recombinant frequency between x and y? Decimal answer only. (Note: there is no crossing over in Drosophila males)

B.)What is the recombinant frequency between x and z? Decimal answer only.

C.)What is the coefficient of coincidence? Decimal answer only.

The progeny males have a different phenotype than the females in all three genes.

Therefore, all of them are on the X chromosome.

The two most frequent phenotypes in the males indicate the genotypes of the Xchromosomes in the female, and the two least frequent phenotypes in the males indicate thegene order.

Gene z is in the middle.

Female parent:   xzy+/x+z+y

F1 male:

430    xzy+       parental

441     x+z+y      parental

39         xzy

30        x+z+y+

32      x+zy+

27       xz+y

1         x+zy          DCO

0           xz+y+        DCO

x-z = (32+27+1)/1000 =6%=6 mu---------------------answer

z-y = (39+30+1)/1000 = 7% = 7 mu------------answer

x-y = 6+7 = 13 mu--------------------answer

c.c. = observed DCO/expected

DCO = 1/0.06*0.07*1000 = 0.238