In a monohybrid cross between two heterozygous pea plants for flower position, 75\% of the… — JAMB UTME

In a monohybrid cross between two heterozygous pea plants for flower position, $75\%$ of the $F_1$ offspring are expected to display the dominant phenotype.

Answer: Answer

Answer

The statement is True.

The statement is accurate because crossing two heterozygous organisms (

Aa \times Aa

) in a standard monohybrid cross with complete dominance results in a

3:1

phenotypic ratio, representing

75\%

dominant and

25\%

recessive phenotypes.

Step-by-Step Solution

Identify the parental genotypes

Both parent plants are heterozygous (

Aa

The stem specifies a monohybrid cross between two plants heterozygous for the trait.

Determine the offspring genotypic distribution using Mendel's Law of Segregation

The gametes (

A

and

a

) segregate to produce offspring with genotypes

AA

Aa

Aa

, and

aa

in a

1:2:1

ratio.

Each parent contributes one allele randomly to each offspring during fertilization.

Calculate the proportion of offspring expressing the dominant phenotype

Dominant phenotypes (

AA

and

Aa

) constitute

3

out of

4

offspring, which equals

75\%

The dominant allele (

A

) completely masks the expression of the recessive allele (

a

) in heterozygous genotypes.

Key Concept

Mendel's Law of Segregation and Monohybrid Cross Ratios

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