Concept Explanation: Mendelian Genetics Cross

This question involves a monohybrid cross between two homozygous parents with different alleles for a single gene. Let's analyze it step by step.

Step 1: Understand the Parental Genotypes

The cross is between AA and aa:

• AA: Homozygous dominant genotype
• aa: Homozygous recessive genotype

Step 2: Determine the Gametes

Each parent produces gametes (sex cells) through meiosis:

• Parent AA produces gametes with only A allele
• Parent aa produces gametes with only a allele

Step 3: Perform the Cross to Get F₁ Progeny

When gametes from both parents combine during fertilization:

All F₁ offspring will receive one A allele from one parent and one a allele from the other parent.

Therefore, the genotype of all F₁ progeny is $Aa$ (heterozygous).

Step 4: Determine the Phenotype

In standard Mendelian inheritance:

• The A allele is dominant
• The a allele is recessive

Since the genotype is heterozygous ($Aa$), the dominant phenotype (A) will be expressed.

Final Answer

The F₁ progeny will be: genotypically Aa, phenotypically A

This corresponds to the last option in your list.

Related Topics

• Mendel's Law of Dominance: In a heterozygous pair of alleles, one allele (dominant) masks the expression of the other (recessive).
• Monohybrid Cross: A genetic cross focusing on a single trait with two contrasting forms.
• Punnett Square: A diagram used to predict the genotypes and phenotypes of a genetic cross.

Key Formulae and Theory

Genotype Notation:

• Homozygous dominant: $AA$
• Heterozygous: $Aa$
• Homozygous recessive: $aa$

Punnett Square for AA × aa cross:

This shows all offspring have Aa genotype.