Question
Question: In a monohybrid cross, what is the ratio of homozygous dominant and homozygous recessive individuals...
In a monohybrid cross, what is the ratio of homozygous dominant and homozygous recessive individuals in the F2 generation?
A. 1:2:1
B. 2:1
C. 1:3
D. 1:1
Solution
A monohybrid cross is a genetic combination of two individuals with homozygous genotypes, or genotypes with entirely dominant or absolutely recessive alleles, which for a certain genetic trait result in opposite phenotypes.
Complete answer: A cross between two pure (homozygous) patterns in which only one of the contrasting characters is studied for their inheritance pattern is called a monohybrid cross. The dominant phenotype in the F2 generation is indicated by 3/4, and 1/4 indicates the recessive phenotype. For eg, the F1 generation was all-round, when round seed lines were crossed with wrinkled seed lines, and the F2 generation showed 3 round phenotypic ratio: 1 wrinkled phenotypic ratio. The F2 generation is created by crossing F1 with each other in plants or animals that cannot self-fertilize.
| Parents | RR | rr |
|---|---|---|
| Gametes | R | r |
| F1 generation | Rr | |
| Selfing of the F1 generation | Rr | Rr |
| F1 gamete | RR | Rr |
| F2 generation | RR | Rr |
| Rr | rr |
Thus, as we can see the ratio of homozygous dominant and homozygous recessive individuals in the F2 generation is 1 (RR): 1(rr).
Hence, the correct answer is option (D).
Note: The mystery of genetics was discovered in the 19th century by Gregor Mendel. By cultivating pea plants, he demonstrated experiments on Pisum sativum (pea plant) and observed various forms of inheritance patterns at different generation levels. He proposed three laws based on the results derived; Law of dominance, the law of segregation and the law of independent assortment.