mosome regions containing sperm-promoting genes. Male sterility is not heritable, but interestingly the fathers of these men have normal Y chromosomes, showing that the deletions are new. There have been no convincing cases of nonsexual phenotypic variants associated with the Y. Hairy ear rims (Figure 2-29) has been proposed as a possibility. The phenotype is extremely rare among the popula-tions of most countries but more common among the populations of India. In some (but not all) families hairy ear rims are transmitted exclusively from father to son. assume that all copies within a cell are identical, but we will have to relax this assumption later. Organelle genes show their own special mode of inheritance called uniparental inheritance; that is, progeny inherit organelle genes exclusively from one parent. In most cases, that parent is the mother: ma-ternal inheritance. Why only the mother? The answer lies in the fact that the organelle chromosomes are lo-cated in the cytoplasm rather than the nucleus and the fact that male and female gametes do not con-tribute cytoplasm equally to the zygote. In the case of
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.