BIOS 220 Study Guide - Final Guide: Ploidy, Aneuploidy
Document Summary
~changes in chromosome number: euploid: organisms with multiples of the basic chromosome set (genome). More/fewer than normal are abberant euploids: abberant euploidy: changes in whole chromosome sets, polyploid: individual organisms that have more than two chromosome sets (triploid 3n, tetraploid 4n, pentaploid, 5n hexaploid 6n). Polyploidy is a naturally occurring process common in plants, rare in animals, and a process that can be manipulated experimentally by treatment with colchicines: autopolyploids: multiple chromosome sets originating from within one species. Triploids (3n) are usually autopolyploids, which arise spontaneously or by cross of a 4n x 2n =3n: characteristically sterile due to unpaired chromosomes at meiosis. When paired homologs (bivalents) segregate to opposite poles, unpaired (univalent) go to one randomly. In a trivalent, a group of 3 are split so a gamete could have either one or two chromosomes making it aneuploid. Autotetraploids can be generated from diploids with the addition of colchicine which disrupts spindle-fiber formation during metaphase and anaphase of mitosis.
