Question

A cross between two individuals who are heterozygous for two genes, one gene with dominant inheritance and the other with codominant inheritance. Assuming independent assortment of the two genes, what phenotypic proportions would be observed in the F1?

A) 3:6:3:1:2:1 B) 16:9:9:3:3:1 C) 12:9:3:1 D) 9:3:3:1 E) 1:1:1:1

Answer 1

Answer:- option A ) 3:6:3:1:2:1 is correct one .

Because the following calculation is done in support of the given answer.

Given that-_-------

Two individuals are heterzygous for two genes, one with dominant inheritance and other with codominant inheritance.

Let the trait be height as dominant inheritance and flower color as codominant inheritance in plant .

Let he trait are controlled as follwing----

Tallness is controlled by H .

Shortness is controlled by h.

Red flower color is controlled by R .

White flower color is controlled by r.

Both Rr produce pink flower as the trait is codominant.

The genotype of the individual to be cross are heterzygous hence it must be

TtRr × TtRr

Phenotype is tall & pink flower.

Gametes of TtRr----) TR, Tr, tR, tr.

Dihybrid cross

Male/ female( cross)	TR	Tr	tR	tr
TR	TTRR (tall,red)	TTRr (tall,pink)	TtRR (tall,red)	TtRr (tall,pink)
Tr	TTRr (tall,pink)	TTrr (tall,white)	TtRr (tall,pink)	Ttrr (tall,white)
tR	TtRR (tall,red)	TtRr (tall,pink)	ttRR (short,red)	ttRr (short,pink)
tr	TtRr (tall,pink)	Ttrr (tall,white)	ttRr (short,pink)	ttrr (short,white)

Phenotypic observation are-------

Tall, red= 3

Tall, pink=6

Tall ,white=3

Short ,red=1

Short ,pink=2

Short,white=1.

Hence the phenotypic ratio is--------- 3:6:3:1:2:1.