BIOL 2500 Lecture Notes - Lecture 6: 5 Fingers, Hearing Loss, Neurodegeneration
Document Summary
Some single-gene mutations are so detrimental that they cause death in the organism. There are caused by lethal mutations, which are inherited as recessive alleles (only the homozygotes die) Lethal alleles can be detected as distortions in segregation ratios caused by one or more missing classes of progeny. Embryonic lethal alleles can be detected by the presence of a 3:1 ratio of living seeds:dead seeds. The living seeds, when planted produce a 2/3 heterozygous: 1/3 homozygous ratio. The sex of an organism can in uence gene expression. Sex limited gene expression is a pattern of expression limited to one sex or the other. The traits involved are called sex-limited traits; both sexes carry the genes for such traits, but they are expressed in just one sex. Mammalian breast and ability to produce milk are female-speci c traits. Horn development is limited to males in some sheep, cows, and other hoofed animals.