Can someone please tell me the phenotypic ratio of trihybrid cross..
The Correct Answer and Explanation is:
In a trihybrid cross, where three traits are being considered, the phenotypic ratio is based on the independent assortment of alleles. Let’s break it down:
Phenotypic Ratio of a Trihybrid Cross:
When considering a trihybrid cross, the typical phenotypic ratio is 27:9:9:9:3:3:3:1. This ratio assumes complete dominance for all three traits.
Explanation:
- Genetic Setup:
In a typical trihybrid cross, each parent is heterozygous for all three traits (e.g., AaBbCc × AaBbCc), where “A,” “B,” and “C” represent dominant alleles, and “a,” “b,” and “c” represent recessive alleles. These three genes assort independently according to Mendel’s Law of Independent Assortment. - Possible Combinations:
Each gene has two possible alleles, so there are 2^3 = 8 possible combinations of alleles for each individual. The dominant phenotype will be expressed when at least one dominant allele is present in the genotype, while the recessive phenotype will only be expressed if the individual has two recessive alleles for that trait. - Phenotypic Categories:
There are 8 possible phenotypic categories, which lead to the 27:9:9:9:3:3:3:1 ratio:- 27 individuals exhibit the dominant phenotype for all three traits.
- 9 individuals show the dominant phenotype for two traits and the recessive for one.
- 9 show the dominant phenotype for two traits and the recessive for one trait.
- 9 display the dominant phenotype for one trait and recessive for the other two.
- 3 exhibit two recessive traits and one dominant.
- 3 show the same combination of two recessive traits.
- 3 display a different combination of two recessive traits.
- 1 shows all three recessive traits.
- Conclusion:
The phenotypic ratio of a trihybrid cross assumes independent assortment of alleles and can be expected to follow the 27:9:9:9:3:3:3:1 pattern for the various combinations of dominant and recessive traits.
