ReasoningModerate1 mark
7(a)
In a homozygous pea plant, axial flowers (A) are dominant over terminal flowers (a).
What is the phenotype and genotype of the F1 generation if a plant bearing pure axial flowers is crossed with a plant bearing pure terminal flowers?
Topic: Monohybrid cross — F1 generation
Previous-year question practice database
Answer
Exam answer
PHENOTYPE: ALL the F1 plants bear AXIAL flowers. GENOTYPE: ALL are Aa — heterozygous dominant.
Explanation
Each parent is PURE (homozygous), so each produces only ONE kind of gamete — A from the axial parent and a from the terminal one. Every offspring therefore receives A from one and a from the other, giving Aa.
They all LOOK axial because A is DOMINANT and masks a — MENDEL’S LAW OF DOMINANCE.
THE POINT WORTH NOTING: every F1 plant CARRIES the allele for terminal flowers, yet none shows it. The recessive allele is MASKED, not lost — which is why terminal flowers reappear in a quarter of the F2 generation.
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