Unit 2 Biology Notes

Unit 2 Biology Notes - Unit 2 Biology Notes I Chapter 8 How...

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I. Unit 2 Biology Notes I. Chapter 8 – How Cells Reproduce a. 8.1 – Overview of Cell Division Mechanisms i. Mitosis is a nuclear division mechanism that occurs in somatic cells (body cells) of multi-celled eukaryotes. It is the basis of increases in body size during growth, replacements of worn-out or dead cells, and tissue repair. ii. Meiosis is a different nuclear division mechanism. It functions only in sexual reproduction, and it precedes the formation of gametes (such as sperm and eggs) or spores. iii. A molecule of DNA and its proteins are one chromosome iv. Each chromosome and its copy stay attached to each other as sister chromatids until late in the nuclear division process. v. A histone-DNA spool is a nucleosome, a unit of structural organization. vi. At this constriction, the centromere, the chromosome’s sister chromatids are attached to each other. vii. SUM IT UP – When a cell divides, each daughter cell receives a required number of chromosomes and some cytoplasm. In eukaryotic cells, this involves nuclear and cytoplasmic division. One nuclear division mechanism, mitosis, is the basis of bodily growth, cell replacements, tissue repair, and often asexual reproduction and eukaryotes. Meiosis, another nuclear division mechanism, is the basis of sexual reproduction. It precedes gamete or spore formation. b. 8.2. – Introducing the Cell Cycle i. A cell cycle is a series of events from one cell division to the next ii. During interphase, a cell increases in mass, roughly doubles the number of its cytoplasmic components, and duplicates its DNA iii. G1 – interval of cell growth and functioning before the onset of DNA replication iv. S – Time of synthesis (DNA replication)
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v. G2 – Second interval after DNA replication when the cell prepares for division vi. Enzymes and other proteins in cells selectively access, activate, and silence information in all that DNA vii. Most of your cells remain in G1 while they are building proteins, carbohydrates, and lipids. Cells destined to divide enter S, when they cp[y their DNA and the proteins attached to it. During G2, they make the proteins that will drive mitosis. viii.Control mechanisms govern the rate of cell division ix. All neurons (nerve cells) in your brain remain in G1 of interphase, and usually they will not divide again x. You cells have a diploid number (2n) of chromosomes; there are two of each type xi. With mitosis, diploid parent cell can produce two diploid daughter cells xii. Mitosis has four stages. All use a bipolar mitotic spindle. This dynamic structure is made of microtubules that grow or shrink as tubulin subunits are added or lost from their ends xiii.SUM IT UP – Interphase, mitosis and cytoplasmic division constitute one turn of the cell cycle. During interphase, a new cell increases its mass, roughly doubles the number of its cytoplasmic components, and duplicates its chromosomes. The cycle ends after the cell undergoes mitosis and then divides its cytoplasm c. 8.3 – A Closer Look at Mitosis
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This note was uploaded on 03/20/2008 for the course BIOL 101 taught by Professor Hogan during the Spring '08 term at UNC.

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Unit 2 Biology Notes - Unit 2 Biology Notes I Chapter 8 How...

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