BISC105 Lecture Notes - Lecture 3: Chromosome, Dosage Compensation, Nondisjunction
14 Mar 2016
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Document Summary
In anaphase lag, only one chromosome is abnormal: the chromosome with monosomy is abnormal. Someone with two+ chromosomal cell types coming from the same genetic origin is a mosaic. Mosaicism results from a postzygotic error due to nondisjunction: ex: 47, xy, +21 in some cells and 46, xy in others, some cells have 2n+1 and some have 2n. Mosaics are less severely affected because they have some normal cells: mosaic down syndrome people function at a high cognitive levels. Nondisjunction can occur at any division of the zygote. Autosomal monosomy is a lethal condition: miscarriages or spontaneous abortion. Some autosomal trisomies are relatively common: most result in spontaneous abortion, three types can result in live births (13, 18, 21, three common features of trisomies are. Growth retardation, mental retardation, and physical abnormalities. Trisomy in chromosome 16 is the most common, followed by 22 and 21.
