DGS 3223 Study Guide - Midterm Guide: Karyotype, Aneuploidy, Sister Chromatids
8 Sep 2016
School
Department
Course
Professor
Document Summary
Whole chromosome probes/paints: cannot be used on interphase nuclei. Combination probes: ratioed probes utilize 2 different colored fluorochromes, each for a different chromosome. Non-disjunction at meiosis ii: failure of sister chromatids to separate, 2 gametes with normal chromosome complent (monosomic, 1 disomic (both from same parent, usually maternal, 1 nullisomic, can stem from increased rates of proximal centromeric recombination. Non-disjunction at mitosis: failure of sister chromatids to separate at mitotic anaphase, results in constitutional mosaicism. 90% of all non-disjunction occurs in meiosis i. 50% of all xxys & trisomy 2s are paternal. Most trisomy 18s result from maternal mii errors. 1/3 of trisomy 21s result from maternal mii errors. Over 90% of all nondisjunction occurs in maternal meiosis. 20% of oocytes have an abnormal chrom : 1-2% of spermatocytes do. Trisomy 16 most common trisomy in sabs: makes up almost 1/3 sabs.
