BIO SCI 97 Lecture 13: Lecture 13 Notes
22 Dec 2018
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Document Summary
Centromeres divide chromosomes into chromosome arms, segments of unequal length. The short arm is called the p arm and the long arm is the q arm. Cytogeneticists are able to identify each chromosome in a karyotype based on size, shape, and banding pattern. The degree of condensation varies from one part of a chromosome to another (euchromatin/ heterochromatin) The standard for human chromosome banding is g (giemsa banding) Triploid plants often infertile as pairing and segregation is disrupted in meiosis (commercially beneficial) In humans, polyploidy is lethal before or shortly after birth. Today the life expectancy is around 60 years and increasingly people with downs syndrome are able to live independent lives. A small number of genes on chromosome 21 are responsible for the cognitive disabilities and heart abnormalities that are principle symptoms. Research has identified a link between the risk of trisomy 21 and maternal age. 90% mortality during the first year of life.
