MBG 2040 Chapter Notes - Chapter 6: Prophase, Apomixis, Fluorescence In Situ Hybridization

• School: University of Guelph
• Department: Molecular Biology and Genetics
• Course: MBG 2040
• Professor: Krassimir Joseph Yankulov

Document Summary

Polyploidy: polyploidy, the presence of extra chromosome sets, is fairly common in plants but very rare in animals. In spite of their robust physical appearance, many polyploid species are sterile: extra sets of chromosomes segregate irregularly in meiosis, leading up to grossly unbalanced (aneuploid) gametes. Zygotes formed by fertilization with such gametes (zero to 3n) are almost certain to die; thus, most triploids are completely sterile. Such a cell will have twice the usual number of chromosomes. Sometimes polyploidization occurs without the separation of sister chromatids. In some somatic tissues - for example, the salivary glands of drosophila larvae - successive rounds of chromosome replication occur without intervening cell divisions and produce large polytene chromosomes that are ideal for cytogenetic analysis. Aneuploidy: aneuploidy describes a numerical change in part of the genome, usually a change in the dosage of a single chromosome. Increased risk is due to factors that adversely affect meiotic chromosome behavior as a woman ages.