Answer:
c. 1:4:6:4:1
Explanation:
The term quantitative heritability refers to the transmission of a phenotypic trait in which expression depends on the additive effect of a series of genes.
Polygenic heritability occurs when a trait results from the interaction of more than one gene. And these genes can also have more than two alleles. The action of many genes and alleles can cause many different combinations that are the reason for genotypic graduation.
Quantitative traits are those that can be measure, such as longitude, weight, eggs laid per female, among others. In the exposed example, the measurable trait is the dog´s friendliness. These characters do not group individuals by any precise and clear categories. Instead, they group individuals in many different categories that depend on how the genes were intercrossed and distributed during meiosis. The result depends on the magnitude in which each allele contributes to the final phenotype and genotype. When they interact, they create a gradation in phenotypes, according to the level of contribution.
In the exposed example, each dominant allele contributes with a higher level of friendliness.
- aabb → 0 = Unfriendly/Loner (although not aggressive);
- Aabb, aaBb → 1 = Somewhat friendly/shy;
- AAbb, AaBb, aaBB → 2 = Friendly;
- AABb, aABB → 3 = Very friendly;
- AABB → 4 = Maximally friendly.
Cross: between two dihybrid friendly dogs
Parentals) AaBb x AaBb
Gametes) AB, Ab, aB, ab
AB, Ab, aB, ab
Punnett square) AB Ab aB ab
AB AABB AABb AaBB AaBb
Ab AABb AAbb AaBb Aabb
aB AaBB AaBb aaBB aaBb
ab AaBb Aabb aaBb aabb
F1) 1/16 AABB ⇒ 4 = Maximally friendly
4/16 AABb + AaBB ⇒ 3 = Very friendly
6/16 AAbb + AaBb + aaBB ⇒ 2 = Friendly
4/16 Aabb + aaBb ⇒ 1 = Somewhat friendly/shy
1/16 aabb ⇒ 0 = Unfriendly/Loner
The Phenotypic ratio is 1:4:6:4:1
