BIO 303 Lecture Notes - Lecture 12: Pseudoautosomal Region, Y Chromosome, Euchromatin
Document Summary
Ex: klinefelter syndrome: xxy karyotype extra x chromosome. Phenotype: tall, large hands/feet, testes can"t produce sperm, not intelligent, breast formation/hips rounded. Ex: turner syndrome: x karyotype missing x not y so only female phenotype is affected. Ovaries non functional, short, undeveloped breasts, flaps of skin, but normal intelligence. Also occurs due to nondisjunction in meiosis. Results in female differentiation, 1/1000 males unaffected. Underdeveloped secondary sex characteristics, sterility, and mental retardation do occur. Males are over 6 feet tall with subnormal intelligence. Absence of y chromosome: female organs start forming. Pseudoautosomal region: present on y chromosomes, shares homology with x chromosome. Pairing region is critical for segregation of x and y chromosomes during male gametogenesis. Msy: male specific region of y: divided equally between euchromatic (functional genes) and heterochromatic regions (lacking genes) Causes undifferentiated gonadal tissue of embryo to form testes. Females with one x chromosome and one y chromosome are missing sry gene.
