Biology 1202B Lecture Notes - Lecture 19: Homologous Chromosome, Ivacaftor, Mutation
15 Oct 2018
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Document Summary
X and y chromosome aneuploidys are more frequent than autosomal aneuploidys; less severe than autosomal aneuploidy. Very little information on the y chromosome. Numerical abnormalities alter gene expression in quantity: changes amount of protein either more or less protein; harmful. Structural abnormalities may do the same: moving gene more closer to the promoter up-regulating that gene, quantity. Trisomy 21: downs syndrome extra chromosome 21. Trisomy is survivable if it is chromosome 21, 18 and 13. 21, 18, 13 have the smallest number of genes. Chromosome with a lot of genes not tolerated. Chromosome with very few genes may be tolerated. Error in meiosis: a gamete is missing a chromosome, failing chromosomes to properly divide. If nondisjunction occurs in meiosis i, both maternal and paternal chromosomes end up in one gamete. If nondisjunction occurs in meiosis ii, chromosomes are not separated normally and one gamete does not get any chromosomes.
