Question

You set up a cross using two corn plants with green seedlings and obtain the following progeny (6 points):

3583 green seedlings

853 white seedlings

260 yellow seedlings

1. Assign genotypes for seedling color
2. What is the hypothesized mode of inheritance for seedling color?

c. Perform a Chi-square analysis to test the hypothesis stated in part (b) of this question

Answer 1

a & b).

3583 : 853 : 260 is more or less to similar witu 12:3:1 ratio. This ratio appears in dominant epistasis.

When a dominant allele at one locus can mask the expression of both alleles (dominant and recessive) at another locus, it is known as dominant epistasis.

Explanation:

Green = A_B_ or A_bb

White = aaB_

yellow = aabb

c).

AaBb (green) x AaBb (green)---Parents

Aa x Aa = A_ (3/4) & aa (1/4)

Bb x Bb = B_ (3/4) & bb (1/4)

A_B_ = 3/4 * 3/4 = 9/16

A_bb = 3/4 * 1/4 = 3/16

Green = A_B_ + A_bb =9/16 + 3/16 = 12/16

White = aaB_ = 1/4 * 3/4= 3/16

Yellow = aabb = 1/4 * 1/4 = 1/16

Expected progeny:

Total progeny = 4696

Green = 12/16*4696 = 3522

White = 3/16 * 4696 = 880.5

Yellow = 1/16 * 4696 = 293.5

Phenotype	Observed(O)	Expected (E)	O-E	(O-E)2	(O-E)2/E
Green	3583	3522	61	3721.00	1.0565
White	853	880.5	-27.5	756.25	0.8589
Yellow	260	293.5	-33.5	1122.25	3.8237
Total	4696	4696			5.7391

Chi-square value = 5.74

Degrees of freedom = no. of phenotypes - 1

DF = 3-1=2

P value = 5.99

The chi-square value of 5.74 is less than the p value of 5.99. Hence, null hypothesis is accepted and the populations support the dominant epistasis mode of inheritance.