One gene determines red vs. white flowers in pea plants, and another determines axial vs. terminal flowers. Two true-breeding stocks of pea plants are crossed. One parent has red, axial flowers and the other has white, terminal flowers; all F1 individuals have red, axial flowers. If you perform a cross between two of these F1 individuals, approximately what fraction of the offspring should have red, axial flowers?

Fraction of the offspring with red, axial flowers is

Explanation:

Let the allele for red flower be represented by "R" and the allele for white flower be represented by "r" and R is a dominant trait over r.

Let the allele for axial flower be represented by "A" and the allele for terminal flower be represented by "a" and A is a dominant trait over a

F1 cross

RRAA * rr aa

RrAa

F2 Cross

RrAa * RrAa

RrAa

RA         Ra         rA     ra

RARRAARRAaRrAARrAa

RaRRAaRRaaRrAaRraa

rARrAARrAarrAArrAa

raRrAaRraarrAa    rraa

Possible genotypes

RRAA - 1

RRAa- 2

RrAA- 2

RrAa- 4

RRaa- 1

Rraa- 2

rrAA- 1

rrAa – 2

rraa- 1

Possible Phenotypes –  

Red & Axial – RRAA, RRAa, RrAA, RrAa

Red & Twisted – Rraa, Rraa

White and Axial – rrAA, rrAa

White and Twisted - rraa

Fraction of the offspring with red, axial flowers is