MCB 10 Lecture 16: MCB10 Lect16 - Chromosomes Pt2, Human Evolution
25 Sep 2016
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Lecture 16 chromosomes (continued) & human evolution: aneuploidy (continued, how nondisjucntion leads to sex chromosomes in aneuploids. Features include: short stature, webbing at back of neck, incomplete sexual development (infertile), impaired hearing. 1 in 2,500 female births; 99% of affected fetuses die in utero. Individuals who are mosaics may have children: triplo-x (xxx syndrome) Few modest effects on phenotype include: tallness, menstrual irregularities, and slight impact on intelligence. 1 in 1,000 female births: x-inactivation of two x chromosomes occurs and cells have two barr bodies, may compensate for presence of extra x, klinefelter syndrome (xxy syndrome) Phenotypes include: incomplete sexual development; rudimentary testes and prostate; long limbs, large hands and feet; some breast tissue development. 1 in 500 male births: most common cause of male infertility, xyy syndrome (jacobs syndrome, modest phenotypes may include: great height, acne, speech and reading disabilities. 1 in 1,000 male births; 96% are phenotypically normal.
