CBSE 2025, Set 2

Question

Using a Punnett square, work out the distribution of an autosomal phenotypic feature in the first filial generation after a cross between a homozygous female and a heterozygous male for a single locus.

Edvaya · Accepted Answer

The correct answer is Subjective. **SOLUTION** Let the dominant allele be $G$ and the recessive allele be $g$. A homozygous female can either be homozygous dominant ($GG$) or homozygous recessive ($gg$). **Scenario 1: Homozygous Dominant Female ($GG$) $	imes$ Heterozygous Male ($Gg$)** * Gametes of Female: $G$, $G$ * Gametes of Male: $G$, $g$ | | $G$ | $g$ | | :--- | :--- | :--- | | **$G$** | $GG$ | $Gg$ | | **$G$** | $GG$ | $Gg$ | **Result:** 100% of the $F_1$ progeny display the dominant phenotype. **Scenario 2: Homozygous Recessive Female ($gg$) $	imes$ Heterozygous Male ($Gg$)** * Gametes of Female: $g$, $g$ * Gametes of Male: $G$, $g$ | | $G$ | $g$ | | :--- | :--- | :--- | | **$g$** | $Gg$ | $gg$ | | **$g$** | $Gg$ | $gg$ | **Result:** 50% display the dominant phenotype ($Gg$) and 50% display the recessive phenotype ($gg$).

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Biology > Reproduction And Genetics > Principles Of Inheritance And Variation

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