In a species of wild mountain cats, males are XY and females are XX. A sex-linked gene on the X chromosome controls coat colour. The allele A A\,A codes for amber coat colour, and the allele C C\,C codes for charcoal coat colour. These alleles are codominant; heterozygous females (XAXCX^A X^CXAXC) exhibit a mottled amber-charcoal coat pattern.
An autosomal gene, which is not sex-linked, interacts with the gene controlling coat colour. The dominant allele I I\,I prevents pigment synthesis, resulting in pure white fur regardless of the sex-linked genotype. The recessive allele i i\,i has no effect on pigment synthesis.
Name the type of gene interaction shown where the autosomal gene masks the expression of the sex-linked gene.
Determine the phenotype (including sex and coat appearance) of a cat with the genotype XAXCiiX^A X^C iiXAXCii.
Complete a genetic diagram to show all the possible genotypes and the ratio of expected phenotypes in the offspring resulting from the cross: XAXAIi×XCYiiX^A X^A Ii \times X^C Y iiXAXAIi×XCYii.
In a population of these cats, 36% of the individuals have the dominant I I\,I allele and have white fur. Use the Hardy–Weinberg equation to calculate the frequency of the recessive allele i i\,i in this population. Show your working.
