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Unformatted text preview: February 3, 2011 Lecture Four Chapter 2: Biology and Behavior What are chromosomes? chromosomes -- long, threadlike molecules made up of DNA DNA carries biochemical instructions involved in the formation and functioning of an organism genes: each segment of DNA that provides the code for specific biochemical in- structions all cells --> 46 chromosomes (23 pairs) the egg and sperm cells --> 23 chromosomes Sex Determination Females have two X chromosome Males have one X chromosome and one Y chromosome Diversity and individuality individuals differ from one another by less than 1.5% of their genes common chromosomes: the chromosomes of humans and mice share many identical blocks of genes (i.e. colored bars) Mechanisms for genetic diversity mutations: changes in sections of DNA caused by random or environmental factors random assortment: the shuffling of the 23 pairs of chromosomes in the sperm and egg crossing over: sections of DNA switch from one chromosome to another during...
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This note was uploaded on 02/08/2011 for the course PS 241 taught by Professor Ganea during the Spring '11 term at BU.
- Spring '11