Question 2 (14 pts) Suppose that gene A is on the X chromosome, and genes B, C,

Question

Question 2 (14 pts) Suppose that gene A is on the X chromosome, and genes B, C, arn d D-. The cross AA BB A- signifies the dominant phenotype. An equivalent situation holds for CC DD females by aY bb cc dd males is made A. What is the frequency of A- individuals in the Fi? Explain. B. What is the frequency of a males in the Fi? Explain. C. What is the Frequency of A- B- C- D- among the females in the F1? Explain D. How many F2 genotypes will there be? Explain E Wh poportion f'he our ) aY F. How often will you obtain each of the following genotypes in the F2: (1) A-bb CC dd (female); (Q BB Cc Dd; (3) AYbb cc dd; (4) aa bb Cc Dd. Show rationale.

Explanation / Answer

AAA BB CC DD X aY bb cc dd

Female x Male

XAXA x XaY

BB X bb

CC X cc

DD x dd

a. The frequency of A individual- 4/4 =1 or 100% A.

B. The frequency of "a" male is 0 as there are no males containing" a "gene". In fact, all the males (50 %here ) will contain A gene.

C.The frequency of A gene in females- all the females will have A gene in the heterozygous condition. (Aa)

The frequency of B gene in females -  all the females will have B gene in the heterozygous condition. ( Bb)
The frequency of C gene in females - all the females will have C gene in the heterozygous condition. (Cc)

The frequency of D gene in females-  all the females will have D gene in the heterozygous condition. (Dd)

D. F2 can be obtained by selfing-

Aa Bb Cc Dd x Aa Bb Cc Dd

Aa x Aa

Bb x Bb

Cc x Cc

Dd x Dd

genotypes- AA, Aa, aa,BB,Bb , bb, CC, Cc, cc, DD, Dd, dd.Thus 12 genotypes would be obtained in f2.

e.heterozygous for Aa -2/4=1/2

heterozygous for Bb  -2/4=1/2

Heterozygous for Cc-  -2/4=1/2

Heterozygous for Dd-  -2/4=1/2

1/2 x 1/2 x 1/2 x1/2 = 1/16

XA XA Xa XAXa XaXA y XAy XAy

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