In polygenic inheritance trait which controlled by three pairs of gene...
Polygenic Inheritance and Phenotypic Ratio
Polygenic inheritance is a type of inheritance where a trait is controlled by multiple genes, each contributing a small effect to the trait. In this type of inheritance, the phenotype of an individual is determined by the cumulative effect of the alleles of multiple genes.
Heterozygous Cross and Phenotypic Ratio
In a heterozygous cross, two individuals that are heterozygous for three alleles are crossed. This means that each individual has two different alleles for each of the three genes that control the trait. When these individuals are crossed, their offspring will inherit a combination of alleles from both parents.
The phenotypic ratio of the offspring is determined by the number of different genotypes that can result from the cross. In this case, the three genes control the trait, and each gene has two alleles. Therefore, there are a total of 2x2x2=8 possible genotypes that can result from the cross.
The phenotypic ratio of the offspring can be calculated by determining the number of different genotypes that produce each phenotype. In this case, the phenotypic ratio is:
1 : 6 : 15 : 20 : 15 : 6 : 1
This means that for every one individual with the extreme phenotype, there are six individuals with a slightly less extreme phenotype, 15 individuals with a moderate phenotype, 20 individuals with a slightly more extreme phenotype, six individuals with a phenotype that is slightly less extreme than the extreme phenotype, and one individual with the extreme phenotype.
Conclusion
In summary, a heterozygous cross between two individuals that are heterozygous for three alleles produces offspring with a phenotypic ratio of 1 : 6 : 15 : 20 : 15 : 6 : 1. This is because polygenic inheritance is determined by the cumulative effect of multiple genes, each contributing a small effect to the trait.
In polygenic inheritance trait which controlled by three pairs of gene...
This type of inheritance is controlled by three pairs of genes that's why correct option is 'D'
(1:2:1 is a phenotypic ratio of co dominance & incomplete dominance / 9:3:3:1 is a ratio of dihybrid cross / 1:4:6:4:1 is a polygenic inheritance controlled by two pairs of genes