Question

In Mendel's pea plants, the genes that code for flower color, seed color and seed shape are on 3 different chromosomes. For flower color, purple is dominant over white, yellow seeds are dominant over green and round seeds are dominant over wrinkled seeds. If you crossed two parents who were heterozygous for all 3 genes, how many purple flowered, round and yellow seeded plants would you expect in the offspring generation? correct answer is 27/64 please show work thank you

Answer 1

Purple colour = P, white colour=p

yellow seeds=Y, green seed=y

round seed=R, wrinkled seed = r

        We are crossing 2 parents who are heterozygous for the 3 genes

                                                          PpYyRr X PpYyRr

Now, we can break them into 3 groups

Pp X Pp

YyX Yy

Rr X Rr

if we cross individual group

Pp X Pp

	P	p
P	PP	Pp
P	Pp	pp

Dominant phenotype ( Purple flower) will be expressed by homozygous PP, and heterozygous Pp

Recessive phenotype ( white flower) will be expressed by homozygous pp

Purple flower: white flower= 3/4:1/4

YyX Yy

	Y	y
Y	YY	Yy
y	Yy	yy

Dominant phenotype ( yellow seed ) will be expressed by homozygous YY, and heterozygous Yy

Recessive phenotype ( green seed) will be expressed by homozygous yy

yellow seed : green seed= 3/4:1/4

Rr X Rr

	R	r
R	RR	Rr
r	Rr	rr

Dominant phenotype ( round seed ) will be expressed by homozygous RR, and heterozygous Rr

Recessive phenotype ( wrinkle seed) will be expressed by homozygous rr

round seed : wrinkle seed= 3/4:1/4

Thus no of purple flowered, round and yellow seeded plants= 3/4 X 3/4 X 3/4 = 27/ 64