BIOL 202 Lecture Notes - Lecture 17: Ploidy, Aneuploidy, Sister Chromatids
20 Feb 2018
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In bees, wasps and ants, females are diploid and males are monoploid: just depends on whether eggs are fertilized or not when they develop. Through a mitosis-like process: the cells already have only one chromosome copy, no need to split them up. Error in first or second division and trisomy 21: 90% of non-disjunction occur in female meiosis: You look at chromosome markers to tell which chromosomes come from which: now, figure out which division is affected: Error in first division: the two chromosome 21 in aneuploid gametes are. Just choose markers close to centromeres (not a lot of recombination here) For an aaa individual gametes can be: parents homologous. 25% of time: a (1/6, a (2/6, aa (2/6, aa (1/6, bridge"s hypothesis. Meiotic pairing in sexual chromosome trisomy (bridges, vermilion-eyed fruit fly experiments) In normal meiotic pairing, x will pair with x or y.
