Final answer:
It is false that the agouti allele shuts down melanin; instead, the agouti allele's expression is masked when the separate C gene is homozygous for the recessive allele, leading to albino mice, irrespective of the A gene's alleles due to epistasis.
Step-by-step explanation:
The concept described in the question relates to epistasis, which is an interaction between different gene loci where one gene masks or suppresses the expression of another. In mice, the agouti coat color (A) is dominant to solid colors, but pigment production is controlled by a separate gene (C). The recessive allele c at the C locus can shut down pigment production, leading to an albino mouse, regardless of the agouti alleles.
The agouti allele does not shut down melanin; rather, it is the C locus that can result in lighter pigmentation when it is homozygous recessive (cc). Therefore, if an agouti (A) allele is present, but the C locus is homozygous recessive (cc), the mouse will be albino because the C gene is epistatic to the A gene.