Question

Cross between which pea plants is considered to be the test cross?

• A. Two dominant plants
• B. Two recessive plants
• C. A dominant and a homozygous recessive plant
• D. A dominant and heterozygous recessive plant

Answer 1

The correct option is C

A dominant and a homozygous recessive plant

The correct option is C.

Explanation of correct option:

1. When a dominant phenotype is crossed with its recessive phenotype then the process is called test cross.
2. The test is performed to identify the zygosity of the dominant phenotype.
3. A test cross is always done with a homozygous recessive plant.

Explanation of incorrect options:

Option A:

1. If two dominant plants are crossed then all genotypes and phenotypes will be dominant.
2. The zygosity therefore can not be identified.
3. The test cross is done to identify the zygosity, therefore two dominant plants can not be crossed.

Option B:

1. If two recessive plants are crossed then all genotypes and phenotypes will be recessive.
2. In case of two recessive plants, they must be homozygous.
3. The zygosity therefore can not be identified.
4. So test cross can not be performed on two homozygous plants.

Option D:

1. There can not be any heterozygous recessive trait.
2. The test cross is done with a heterozygous dominant trait and homozygous recessive trait to identify the zygosity.
3. So, a homozygous recessive plant is used in it.

Final answer: Cross between a dominant and a homozygous recessive pea plant is considered to be the test cross.