North American wolves can have gray fur or black fur. A single gene with two alleles codes for fur color. Information about the fur color of parents and offspring in four wolf families is shown below.
Family
1 | gray fur x black fur | 3 gray fur : 2 black fur
2 | gray fur x black fur | 0 gray fur : 5 black fur
3 | black fur x black fur | 1 gray fur : 3 black fur
4 | gray fur x gray fur | 4 gray fur : 0 black fur
a. Identify the most likely inheritance pattern (dominant-recessive, incomplete dominance, codominance, sex-linked, polygenic, multiple alleles) for fur color in wolves.
b. Explain how the information about family 3 supports the inheritance pattern you identified in part (a).
Comparing families 1 and 2 allows us to make a hypothesis that it is a case of dominant/recessive, which can be confirmed with families three and four.
Feel free to propose a scenario for discussion.
2 | gray fur x black fur | 2 gray fur : 3 black fur. <==== thought I saw this as part of the answer stem.
To answer part (a) of the question, we need to analyze the information about the fur color of parents and offspring in the four wolf families provided.
In family 1, when a wolf with gray fur (Gg) is crossed with a wolf with black fur (gg), the offspring ratio is 3 gray fur : 2 black fur.
In family 2, when a wolf with gray fur (Gg) is crossed with a wolf with black fur (gg), the offspring ratio is 0 gray fur : 5 black fur.
In family 3, when two wolves with black fur (gg) are crossed, the offspring ratio is 1 gray fur : 3 black fur.
In family 4, when two wolves with gray fur (Gg) are crossed, the offspring ratio is 4 gray fur : 0 black fur.
Based on this information, we can observe that:
- When a wolf with gray fur (Gg) is crossed with a wolf with black fur (gg), the offspring have a combination of gray and black fur, suggesting that the gray fur allele is dominant to the black fur allele.
- However, when two wolves with black fur (gg) are crossed, the offspring have a mix of black and gray fur, indicating that the black fur allele is not completely recessive.
From this analysis, we can conclude that the inheritance pattern for fur color in wolves is likely incomplete dominance. In incomplete dominance, neither allele is completely dominant over the other, and the offspring show a blend or intermediate phenotype.
Moving on to part (b) of the question, family 3 provides supporting evidence for the identified inheritance pattern. When two wolves with black fur (gg) are crossed, the offspring exhibit a mix of black and gray fur in a ratio of 1 gray fur : 3 black fur. This ratio supports the idea of incomplete dominance, as the offspring do not have only black fur (as would be expected in a complete-recessive scenario), but also have gray fur suggesting a blending of the two alleles.
Therefore, the information from family 3 aligns with the inheritance pattern identified in part (a), which is incomplete dominance.