Question

When a tall pea plant with round seeds was selfed, it produced the progeny of
(a) Tall plants with round seeds and
(b) Tall plants with wrinkled seeds.
Identify the genotype of the parent plant.

• A. TtRr
• B. TtRR
• C. TTRR
• D. TTRr

Answer 1

The Correct Option is D

Analysis of the provided data:
Trait for height: Tall (T) is dominant over dwarf (t).
Trait for seed shape: Round (R) is dominant over wrinkled (r).
The parent plant exhibits tall stature and round seeds. The presence of offspring with wrinkled seeds (rr) indicates the parent plant carries the recessive allele for seed shape (r). The absence of dwarf offspring implies the parent plant possesses at least one dominant allele for height (T).

Observed offspring phenotypes:
Tall, Round: Possible genotypes include TTRR, TTRr, TtRR, or TtRr.
Tall, Wrinkled: The genotype must be Ttrr.

The requirement for both round and wrinkled seed production necessitates a heterozygous genotype for seed shape (Rr) in the parent. As all offspring display tall stature, and wrinkled offspring are present, the parent plant must be homozygous dominant for height (TT). If the parent had been heterozygous for height (Tt), dwarf offspring (tt) would have been observed, which is not the case.
Consequently, the parent’s genotype is determined to be TTRr.