Lecture 20-W11 - Lecture 20 (2-25-11) Notes I. Introduction...

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Lecture 20 (2-25-11) Notes I. Introduction to the cell cycle and mitosis A. Purpose of the cell cycle and mitosis 1. To create two daughter cells that have the same genetic material as the mother cell 2. This requires replication of the mother cells DNA and an even division of the DNA during mitosis B. Mitosis versus meiosis 1. Higher eukaryotes are diploid (two copies of each chromosome) 2. Meiosis creates specialized cells called gametes (e.g., eggs or sperm) that contain only one copy of each chromosome 3. Mitosis occurs in somatic cells (which form the body and do not directly contribute to the next generation); daughter cells are diploid like the mother cells. C. Chromosomes 1. DNA plus associated proteins 2. During interphase (any stage except mitosis) chromosomes are relatively loose jumbles of DNA (like a bowl with a few really long spaghetti) 3. after replication, there are two strands of spaghetti 4. at the start of mitotis, the chromosomes undergo dramatic condensation so that they are 10000 times shorter than before. Each replicated chromosome has two sister
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Lecture 20-W11 - Lecture 20 (2-25-11) Notes I. Introduction...

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