ReasoningModerate1 mark
6(a)
In Mendel’s experiments, tall pea plants (T) are dominant over dwarf pea plants (t).
What is the phenotype and genotype of the F1 generation if a homozygous tall plant is crossed with a homozygous dwarf plant?
Topic: Monohybrid cross — F1 generation
Previous-year question practice database
Answer
Exam answer
PHENOTYPE: ALL the F1 plants are TALL. GENOTYPE: ALL are Tt (heterozygous).
Explanation
Each parent is homozygous (TT and tt), so each produces only ONE kind of gamete — T and t. Every offspring therefore receives T from one parent and t from the other, giving Tt.
They all LOOK tall because T is DOMINANT and masks t. This is MENDEL’S LAW OF DOMINANCE.
THE POINT WORTH NOTING: every F1 plant CARRIES the allele for dwarfness, yet none shows it. The recessive allele is MASKED, not lost — which is why dwarfness reappears in a quarter of the F2 generation.
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