Question

A cross between two tall pea plants resulted in offspring having a few dwarf plants. The gene-combination of the parental plants must be

• A. Tt and Tt
• B. Tt and tt
• C. TT and tt
• D. TT and Tt

Answer 1

The Correct Option is A

Step 1: Height Inheritance in Pea Plants:
Pea plant height is determined by a pair of alleles: T (tall) and t (dwarf). Tallness is dominant, meaning at least one T allele results in a tall plant.

Step 2: Offspring Analysis:
If crossing two tall pea plants produces dwarf offspring, both parents must carry the recessive dwarf allele (t). Dwarfism (tt) requires both parents to contribute a t allele.

Step 3: Parent Genotype Determination:
Dwarf offspring (tt) can only arise from tall parents if both parents are heterozygous (Tt). This genotype allows for the transmission of both dominant (T) and recessive (t) alleles.
- Possible offspring genotypes from Tt x Tt cross:
- TT (tall),
- Tt (tall),
- tT (tall),
- tt (dwarf).

Step 4: Conclusion:
Since both tall and dwarf offspring are possible, the parental genotype combination must be Tt and Tt.