Question

3) A corn plant with purple, full kernels is crossed with a plant having purple, full kernels. The following progeny are obtained: Purple, full 100 Purple, shrunken 36 Yellow, full 30 Yellow, shrunken 8 Determine the genotypes of the parents and progeny. Test your hypothesis with a Chi square test until it is accepted.

Answer 1

since both parents are having purple full kernels and progenies have purple full, purple shrunken, yellow full and yellow shrunken and phenotypic ratio of progeny is

purple full: purple shrunken: yellow full: yellow shrunken=100:36:30:8

=12.5:4.5:3.75:1

so this appears like Parents are heterozygous for both traits

Null hypothesis H0= Parents are the heterozygous ( P for purple p for yellow and F for full and f for shrunken so parents are PpFf)

the expected phenotypic ratio of progenies of PpFf*PpFf

is Purple full: Purple shrunken: yellow full: yellow shrunken=9:3:3:1 ( this is the expected ratio from a dihybrid cross)

Phenotype	expected ratio(E)	observed ratio(O)	(E-O)^2/E
Purple full	9	12.5	1.36
purple shrunken	3	4.5	0.5
yellow full	3	3.75	0.15
yellow shrunken	1	1	0
		chi-square value	2.01

here degrees of freedom= number of phenotypes-1

= 4-1

=3

for degrees of freedom 3 and p<0.05 value from chi-square table is 7.815 which is greater than our chi square value( 2.01_

so we accept our null hypothesis that is both parents are heterozygous PpFf