Question

In a monohybrid cross between two heterozygous parents (\(Aa \times Aa\)), what is the genotypic ratio among the offspring?

• A. 1:1.
• B. 1:2:1.
• C. 3:1.
• D. 9:3:3:1.

Hint:

In a monohybrid cross between heterozygous parents, the genotypic ratio is always \(1:2:1\), while the phenotypic ratio is \(3:1\).

Answer 1

The Correct Option is B

Phase 1: Punnett Square Construction.
Parental genotypes are \(Aa\) and \(Aa\). The Punnett square is constructed as follows:\[\begin{array}{c|c|c} & A & a
\hlineA & AA & Aa
a & Aa & aa
\end{array}\]Phase 2: Genotypic Ratio Determination.
Offspring genotypes observed in the Punnett square are: \(AA\): 1. \(Aa\): 2. \(aa\): 1.The resulting genotypic ratio is:\[1 : 2 : 1.\]Phase 3: Option Analysis.
Option (A): Incorrect. This signifies an equal distribution between two genotypes, which is not accurate. Option (B): Correct. The genotypic ratio for a monohybrid cross is \(1:2:1\). Option (C): Incorrect. This represents the phenotypic ratio, not the genotypic ratio. Option (D): Incorrect. This represents the phenotypic ratio for a dihybrid cross, not a monohybrid cross.\[\therefore \text{The accurate genotypic ratio is: } 1 : 2 : 1.\]