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: Understanding the Inheritance of Height in Pea Plants:
In pea plants, the height trait is controlled by a pair of alleles: T for tall and t for dwarf. The tall trait is dominant over the dwarf trait. This means that a plant with at least one dominant allele (T) will be tall.

Step 2: Analyzing the Offspring:
When two tall pea plants are crossed, but some offspring are dwarf, it indicates that both parent plants must carry the recessive dwarf allele (t) in their genotype. For a dwarf plant to be produced, both parents must contribute the recessive allele t.

Step 3: Determining the Parent Genotype:
The only way to produce dwarf offspring (tt) from tall plants is if both parents have a heterozygous genotype (Tt), as this allows for the possibility of both dominant (T) and recessive (t) alleles being passed on.
- If both parents are Tt, their possible offspring genotypes would be:
- TT (tall),
- Tt (tall),
- tT (tall),
- tt (dwarf).

Step 4: Conclusion:
The gene combination of the parental plants must be Tt and Tt, as this allows for the possibility of producing both tall (Tt, TT) and dwarf (tt) offspring.