Name: Test Cross Reveals Genotype
Uploaded: 2019-07-19
Duration: 4 min 37 s
Description: A dominant trait can have two types of genotype. What are these genotypes? And is there a test to identify them? Learn a test cross to reveal the genotype of...

Question

Explain the law of dominance using a monohybrid cross.

Accepted Answer

Mendel’s law of dominance states that out of a pair of contrasting characters only one is dominant whereas the other is recessive. A dominant allele expresses itself in a monohybrid cross and suppresses the expression of the recessive allele. However, this recessive allele for a character is not lost and remains hidden or masked in the progenies of F₁ generation and reappears in the next generation.

Example: A cross between a Tall and Dwarf plant, with Tall being dominant allele.

The phenotypic ratio is 3: 1, i.e., there are three tall plants and one dwarf plant obtained at the end of F₂ generation and the genotypic ratio is 1:2:1, which means that 1 homozygous tall plant, 2 heterozygous tall plants, and 1 homozygous dwarf plant were obtained from the F₂ generation.
We can observe that in the F₂ generation, both the alleles, tall and dwarf are expressed whereas, in the F₁ generation, only dominant allele, tall was expressed.

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