Question

A test cross is performed between a tall flower and a short flower. The offspring have two distinct phenotypes. Scientist A concludes that this means that one parent must be homozygous recessive while the other parent is homozygous dominant. Scientist B concludes that this means that one parent must be homozygous recessive while the other parent is heterozygous. Which scientist is correct and what percentage of each phenotype will be the result?

A. Scientist A is correct because when a homozygous dominant parent is crossed with a homozygous recessive parent, the resulting offspring will be 75% tall, 25% short.
B. Scientist A is correct because when a homozygous dominant parent is crossed with a homozygous recessive parent, the resulting offspring will be 50% tall, 50% short.
C. Scientist B is correct because when a homozygous recessive parent is crossed with a heterozygous parent, the resulting offspring will be 75% tall, 25% short.
D. Scientist B is correct because when a homozygous recessive parent is crossed with a heterozygous parent, the resulting offspring will be 50% tall, 50% short.

Answer 1

Scientist B is correct because a test cross between a homozygous recessive parent and a heterozygous parent will result in a 1:1 phenotypic ratio of tall to short offspring, signifying a 50% tall and 50% short distribution.

Step-by-step explanation:

The correct scientist is Scientist B as they assert that a cross between a homozygous recessive parent and a heterozygous parent will result in offspring with a 50% tall phenotype and a 50% short phenotype. The option that fits this description is D.

This outcome is explained by a Punnett square, which predicts a 1:1 phenotypic ratio for such a cross, where T represents the dominant tall allele and t represents the recessive short allele.

In this cross (Tt x tt), the heterozygous (Tt) parent can provide a T (tall) or t (short) allele, while the homozygous recessive (tt) parent can only contribute a t (short) allele, resulting in half of the offspring being Tt (tall) and half being tt (short).

In this test cross, Scientist B is correct because one parent must be homozygous recessive while the other parent is heterozygous. When a homozygous recessive parent is crossed with a heterozygous parent, the resulting offspring will be 50% tall and 50% short. This is due to the inheritance pattern of a dominant-recessive trait.