BIOL 039 Lecture Notes - Lecture 11: Agouti Gene, Moe Williams, Neurodegeneration
Document Summary
Some single-gene mutations are so detrimental that they cause death in the organism. Inherited as recessive alleles (only the homozygote die) Can be detected as distortions in segregation ratios caused by one or more missing classes of progeny. Produced by a combination of yellow and black pigments along each hair. Dominant allele of agouti, a^y, causes yellow pigment to be deposited along the entire hair, resulting in a yellow coat. The a^y allele is recessive embryonic lethal, so all yellow mice are heterozygous. In other words: agouti is a recessive allele (aa). A^y code for yellow hairs but homozygote for ay is lethal. The ay mutation is caused by a deletion that affects two genes, Raly produces a protein essential for mouse development; the deletion connects the raly promoter to the agouti gene. In heterozygotes, an excess of yellow pigment is produced, whereas homozygotes die due to lack of the raly protein.
