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Sex-Linked Traits. Ch. 10.5. Sex-Linked Genes. Sex chromosomes: X and Y (male: XY, female: XX) Offspring sex depends on whether the sperm cell that fertilizes the egg carries an X or a Y Sex-linked gene = any gene that is located on a sex chromosome (most found on the X chromosome).
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Sex-Linked Traits Ch. 10.5
Sex-Linked Genes • Sex chromosomes: X and Y (male: XY, female: XX) • Offspring sex depends on whether the sperm cell that fertilizes the egg carries an X or a Y • Sex-linked gene = any gene that is located on a sex chromosome (most found on the X chromosome)
Discovery of Sex-Linked Genes • Thomas Morgan discovered sex-linked genes while studying eye color in fruit flies • White eyes are rare in fruit flies (most have red eyes)
White Eye Color Inheritance in Drosophila Summary: P: XRXRx XrY F1: 2XRXr, 2XRY F2: XRXR, XRXr, XRY, XrY Conclusion: The gene involved in eye color is on the X chromosome!
Sex-Linked Disorders • Color blindness, mostly in males • color blindness test • FYI: • Achromatopsia - complete color blindness, seeing only shades of gray • Deuteranopia - difficulty telling the difference between red/purple and green/purple • Protanopia - difficulty telling the difference between blue/green and red/green • Tritanopia - difficulty telling the difference between yellow/green and blue/green)
Sex-Linked Disorders Continued… • Hemophilia, (blood fails to clot) • Much more common in males!