Monohybrid Cross

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The gene RSPO2 encodes a signaling protein that determines a hair phenotype called "furnishings" in dogs (Cadieu et al, 2009 Science). Furnishings refers to a longer length of hair around the mouth and eyes of the dog. The furnishings phenotype is dominant and is caused by an 167bp insertion within the 3' UTR sequence of the RSPO2 gene. For this question, designate the recessive allele RSPO2⁺ and the dominant allele RSPO2¹⁶⁷.

A. If a true-breeding dog with furnishings is crossed with a true-breeding dog without furnishings, what are the genotypes and phenotypes of the offspring (F₁ generation)?

B. Draw a Punnett Square showing a cross between two F₁ offspring. What are the genotype and phenotype ratios of the F₂?

C. Reviewing what you know about the role of 3' UTR sequences, provide a possible molecular explanation for why the insertion allele is dominant.