Question

You wish to determine whether a tall pea plant is homozygous or heterozygous for tallness. What

cross should you perform to arrive at your answer? Explain your choice of cross.

Answer 1

Bb x Bb or BB x BB or bb x bb

Step-by-step explanation:

B for dominant

b for recessive

When an organism is heterozygous and is crossed, 2 of the offspring out of the 4 will also share the same trait. So, if two of the tall pea plants are crossed, if they are heterozygous 2 of their offspring will also be tall pea plants and if they are homozygous all of their offspring will be tall pea plants.

Cross:

Bb is the tall pea plant if it is heterozygous.

Bb x Bb

B b B B

B BB Bb for homozygous : B BB BB

b Bb bb B BB BB

2/4 are tall pea plants all are tall pea plants

You could pick either cross, they both will give you the right answer answer:

If you use a heterozygous cross and 2 offspring are tall pea plants (same as the parents) then the trait is heterozygous.

If you use a homozygous cross and all offspring are tall pea plants (same as the parents) then it is homozygous.

Note that if the heterozygous cross doesn't have 2 tall offspring then it is homozygous and similarly if the homozygous crossed offspring does not yield all tall pea plants then the gene is heterozygous.