In a monohybrid cross between two heterozygous green-pod pea plants (Gg), Mendel's Law of … — JAMB UTME

In a monohybrid cross between two heterozygous green-pod pea plants ( $Gg$ ), Mendel's Law of Segregation predicts that $75\%$ of the $F_2$ offspring will possess the heterozygous ( $Gg$ ) genotype.

Answer: Answer

Answer

False

The statement is false because a monohybrid cross of two heterozygous individuals (

Gg \times Gg

) yields a genotypic ratio of

1\ GG : 2\ Gg : 1\ gg

. Exactly

50\%

(

2

out of

4

) of the

F_2

offspring inherit the heterozygous genotype (

Gg

). The claimed

75\%

proportion applies to the dominant phenotype, improperly interchanging genotypic composition with phenotypic expression.

Step-by-Step Solution

Identify parental genotypes and apply Mendel's First Law

Both parents are heterozygous (

Gg \times Gg

). During gamete formation, alleles segregate so each gamete receives either

G

g

with equal probability (

50\%

Mendel's Law of Segregation states that allele pairs separate during gametogenesis.

Determine expected offspring genotypic proportions

Random combination of gametes yields

1/4\ GG

2/4\ Gg

, and

1/4\ gg

. The genotypic ratio is

1 : 2 : 1

A standard Punnett square for a monohybrid cross combines

G

and

g

alleles from both parents.

Evaluate the statement's genotypic percentage claim

The heterozygous (

Gg

) fraction is

2/4

, which equals

50\%

. The

75\%

value corresponds to the dominant phenotype (

GG + Gg = 25\% + 50\% = 75\%

The statement incorrectly equates the dominant phenotypic percentage (

75\%

) with the heterozygous genotypic percentage (

50\%

Key Concept

Mendel's Law of Segregation and Monohybrid Genotypic vs Phenotypic Ratios

Estimated Time:1m 30s

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