BIOL 150B Lecture Notes - Lecture 12: Down Syndrome, Nondisjunction, Meiosis
19 Feb 2018
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Karyotype is a display of an individual"s chromosomes. It is often used to detect chromosome errors or imbalances. Errors in meiosis may lead to offspring with genetic disorders (down syndrome has three chromosomes (trisomy 21) 47 chromosomes per cell) Nondisjunction is in meiosis i and meiosis ii. ****if you could choose one stage not to nondisjunction in, it would be meiosis ii**** Nondisjunction of sex chromosomes rarely affect survival of offspring. (turner syndrome in females (xo) Alterations of chromosome structure may lead to disorders. Prior to mendel there were very little studies on heredity, and people did not understand how we passed things down. It is 25% purple 25% white and 50% big pea little pea. It is always a 3/1 ratio *** you must know this. Alternative versions of genes are called alleles. For each character, and organism inherits two alleles, one from each parent. An organism that has two of the same alleles is known as a homozygous.
