Question

In peas, long stem (A) is dominant over short stem (a). A heterozygous, long stem plant (Aa) is crossed with a homozygous, short-stemmed plant (aa). What percentage of plants will be heterozygous for long stem?

Options:
Option 1: 0%
Option 2: 25%
Option 3: 50%
Option 4: 100%

Answer 1

When a heterozygous long stem pea plant (Aa) is crossed with a homozygous short-stemmed plant (aa), 50% of the offspring will be heterozygous (Aa) for the long stem trait.

Step-by-step explanation:

The question asks about the percentage of plants that will be heterozygous for the long stem trait when a heterozygous long stem plant (Aa) is crossed with a homozygous short-stemmed plant (aa).

Using a Punnett square, we can determine the genotypes of the potential offspring from this cross:

• Parental genotypes: Aa (heterozygous long) x aa (homozygous short)
  
• Gametes from Aa parent: A and a
  
• Gametes from aa parent: a and a
  
• Possible offspring genotypes: Aa and aa
  

The possible genotypes of the offspring are Aa (heterozygous long stem) and aa (homozygous short stem), each with a probability of 50%. Therefore, after the cross, 50% of the plants will be heterozygous for the long stem trait.

The correct answer is Option 3: 50%.