Some loci are linked on the sex chromosomes and are described as sex-linked
Female mammals & Drosophila are XX (homogametic):
they have two alleles for any sex-linked locus
Male mammals & Drosophila are XY (heterogametic):
they have a single allele for any sex -linked locus
X-linked genes are inherited in characteristic patterns that differ between sexes
Ex.: Drosophila have four pairs of chromosomes
A white-eye mutant of Drosophila was the first known sex-linked mutant (MGA2 5-08)
First cross: white-eyed male x red-eyed female
Reciprocal cross: white-eyed female x red-eyed male
Other sex determining mechanisms exist in other species
WZ females & ZZ males in birds
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©2006 by Steven M. Carr