Santolaya - Meiosis and Common Chromosomal Abnormalities

Question 1

Nondisjunction in meiosis II

Answer 1

Failure of one sister chromosome to separate. Leads to two normal gametes, one disomic (but two sister chromatids, i.e. maternal or paternal) and one empty. Especially relevant if XX or XY

Question 2

Klinefelter Syndrome

Answer 2

47, XXY. 1/1000 males, tall, hypogonadism, social issues. Increased X beyond 2 increases mental retardation.

Question 3

Turner’s Syndrome

Answer 3

45, X0. Gonadal dysgenesis, short stature

Question 4

Trisomy Rescue (Uniparental Disomy)

Answer 4

When trisomic embryo, but monosomatic gamete chromosome is lost. restores disomy, but can cause mosaicism, male–>male X-linked inheritance

Question 5

Nondisjunction in Meiosis I

Answer 5

homologous chromosomes fail to separate, end up with two empty gametes and two with one of each homologous chromatid