The genotype of a plant showing the dominant phenotype can be determined by :a)Back crossb)Test crossc)dihybid crossd)Pedigree analysisCorrect answer is option 'B'. Can you explain this answer?

Question

Answer

Answer

In genetics a test cross first introduced by Gregor Mendel, involves the the breeding of an individual with a phenotypically recessive individual, in order to determine the zygosity of the former by analyzing proportion of offspring phenotype, zygosity can either be heterozygous and homozygous

Answer

The genotype of a plant showing the dominant phenotype can be determined by test cross.

Test cross is a genetic cross used to determine the genotype of an organism that exhibits a dominant phenotype but has an unknown genotype. It involves crossing the organism with a known homozygous recessive individual for the same trait.

Procedure:
1. Take the plant with the dominant phenotype and cross it with a homozygous recessive individual for the same trait.
2. The resulting offspring will show the dominant phenotype if the tested organism is homozygous dominant (DD) or heterozygous (Dd).
3. On the other hand, if the tested organism is homozygous recessive (dd), all the resulting offspring will exhibit the recessive phenotype.

Explanation:
When a plant shows a dominant phenotype, it can be either homozygous dominant (DD) or heterozygous (Dd) for that particular trait. By performing a test cross, we can determine the genotype of the plant. Here's how:

- If the plant is homozygous dominant (DD):
- In a test cross with a homozygous recessive individual (dd), all the offspring will be heterozygous (Dd) and show the dominant phenotype. This is because the dominant allele (D) will mask the expression of the recessive allele (d).

- If the plant is heterozygous (Dd):
- In a test cross with a homozygous recessive individual (dd), half of the offspring will be homozygous dominant (DD) and show the dominant phenotype, while the other half will be heterozygous (Dd) and also show the dominant phenotype. This is because the dominant allele (D) is present in both cases and masks the expression of the recessive allele (d).

- If the plant is homozygous recessive (dd):
- In a test cross with a homozygous recessive individual (dd), all the offspring will be homozygous recessive (dd) and exhibit the recessive phenotype. This is because both the tested plant and the recessive individual carry the recessive allele (d) and there is no dominant allele to mask its expression.

Therefore, by observing the phenotypes of the offspring resulting from a test cross, we can determine the genotype of the plant showing the dominant phenotype.

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