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Sex Linked Traits. Traits carried on the sex chromosomes. Sex Chromosomes v. Autosomes. Sex chromosomes determine gender; Autosomes are all other chromosomes XX are females XY are males Chickens and moths: males have identical sex chromosomes and females are different
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Sex Linked Traits Traits carried on the sex chromosomes
Sex Chromosomes v. Autosomes • Sex chromosomes determine gender; Autosomes are all other chromosomes • XX are females • XY are males • Chickens and moths: males have identical sex chromosomes and females are different • Most plants and some fish lack sex chromosomes • Some worms depend on the number of chromosomes • Turtles, lizards, and crocodilians are temperature dependent. • In mammals, the Y carries the Sex-determining Region Y (SRY). This codes for the gonads to develop into testes. All other sex linked genes are on the X chromosome.
Thomas Hunt Morgan • Worked with fruit flies • 4 pairs of chromosomes • 3 pairs identical in both genders; 1 pair was different • XX females and XY males • Noticed that there was one fly with white eyes • Crossed a red with a white – all offspring were red • Cross two of those red – ¾ red and ¼ white – all of the white were male • Concluded that the gene for eye color was on the x chromosome • Called a sex-linked trait