Final answer:
The most likely mode of inheritance for coat color in these horses is incomplete dominance.
Step-by-step explanation:
The most likely mode of inheritance for coat color in these horses is d. incomplete dominance. Here's why:
Golden trait expressed in offspring: When a white and a brown horse breed, the offspring are golden, indicating that neither color completely dominates the other. This is a characteristic of incomplete dominance.
Probability of offspring colors: The provided probabilities (25% white, 50% golden, 25% brown) suggest a 1:2:1 ratio for genotypes. This ratio is common in incomplete dominance, where the heterozygous offspring express a blended phenotype between the two parental phenotypes.
No sex-linkage or complete dominance: The probability distribution doesn't favor one sex over the other, eliminating sex-linked inheritance. Additionally, neither parent's color completely disappears in the offspring, ruling out complete dominance.
Polygenic inheritance is possible but less likely: While polygenic inheritance can also explain the observed ratios, it usually involves multiple genes interacting, leading to a wider range of coat colors and not a clear 1:2:1 pattern.
Therefore, based on the available information, incomplete dominance appears to be the most likely mode of inheritance for coat color in these horses.