Question

In one type of plant, orange petals (O) are dominant over yellow petals (o) and tall stems (T) are dominant over short stems (t). Complete a dihybrid cross for parents with the genotypes: OOTt × OoTt and answer the following in complete sentences.

Describe how you would set up a Punnett square for this cross.
List the likelihood of each possible offspring genotype.
List the likelihood of each possible offspring phenotype.

Answer 1

A Punnett square without interaction between genes is shown as follows:

OT Ot OT Ot
OT OOTT OOTt OOTT OOTt
oT OoTT OoTt OoTT OoTt
OT OOTT OOTt OOTT OOTt
ot OoTt Oott OoTt Oott

Summary:
Genotype probability phenotype
OOTT 4/16 = 1/4 orange/tall
OOTt 4/16 = 1/4 orange/tall
OOtt 0/16 = 0 orange/short
OoTT 2/16 = 1/8 orange/tall
OoTt 4/16 = 1/4 orange/tall
Oott 2/16 = 1/8 orange/short
ooTT 0 yellow/tall
ooTt 0 yellow/tall
oott 0 yellow/short
(Total 1)

Therefore the phenotype distribution is as follows:
phenotype probability
orange/tall 1/4+1/4+1/8 = 7/8
orange/short 1/8
yellow/tall 0
yellow/short 0
(Total 1)