Section 5.3 shrunken endosperm (sh), and in 19. Waxy endosperm (wx), recessive g

Question

Section 5.3 shrunken endosperm (sh), and in 19. Waxy endosperm (wx), recessive genes yellow seedling (v) are encoded by three corn plant corn that are linked on chromosome 5. A homozygous for all three recessive alleles is crossed with a plant homozygous for all the dominant alleles. The resulting F1 are then crossed with a plant homozygous for the recessive alleles in a three-point testcross. The progeny of the testcross are: 87 sh Sh Wx 3,479 Sh Wx 3,478 sh WX 1,515 sh Wx 1,531 Wx Sh 292 Sh 280 Wx sh 10,756 Total a. Determine the order of these genes on the chromosome b. Calculate the map distances between the genes. c. Determine the coefficient of coincidence and the interference among these genes

Explanation / Answer

(a). the non recombinant are Wx Sh V and wx sh v

double crossover are- wx sh V and Wx Sh v

   according to above , we can find that they are differ only at the v loci, so v must be the situated in middle.

(b). Wx-V distance - recombinant are wx V and Wx v

   RF= (292+280+87+94) / 10756

   =.07 =7%

   = 7 mu

Sh - V Distance - recombinant are sh V and Sh v

RF' = (1515+1531+87+94) / 10756 = 30 = 30%= 30 mu

the WX - Sh Distance is total of these distances = 7+30 = 37 mu

(c). Expected dcos = RF * RF' * TOTAL PROGENY

= .07(.30)(10756) = 226

C.o. C = OBSERVED DCOS/ EXPECTED DCOS= (87+94)/226=0.80

INTERFERENCE= 1- CoC= 0.20

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