Solomon IM Ch 10

Solomon IM Ch 10 - Chapter10:Chromosomes,Mitosis,andMeiosis...

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Chapter 10: Chromosomes, Mitosis, and Meiosis 93 10 Chromosomes, Mitosis, and Meiosis Lecture Outline I. Eukaryotic chromosomes contain DNA and proteins. A. The chromosomes carry the genetic information in eukaryotes. B. The chromosomes are so named because they may be stained by certain dyes. 1. Chromosomes are composed of chromatin, which is composed of proteins and DNA. a) When cells are not dividing, the genetic material is decondensed, called chromatin. b) Chromosomes condense (become visible as distinct structures) when the cell divides. C. DNA is organized into informational units called genes. 1. Chromosomes contain hundreds to thousands of genes. 2. The Human Genome Project estimates that humans have less than 30,000 genes that code for proteins. D. DNA in chromosomes is packaged in a highly organized way. 1. The genome of E. coli consists of about 4 x 10 6 base pairs, about 1.35 mm in length. 2. The haploid DNA of a human cell is made of 3 x 10 9 base pairs, about 1 m (over 3 ft.) in length. 3. In eukaryotes, DNA is associated with positively charged histone proteins to form beadlike nucleosomes. a) Each nucleosome is composed of 146 base pairs wrapped around 8 histones. b) Scaffolding proteins that are nonhistone proteins aid in the formation of chromosomes. c) There is also a linker segment of DNA and another histone that is not part of the nucleosome but is important in the structure of the chromosome. 4. Histones are not just structural components; they are functional as well. 5. Nucleosomes are part of the chromatin and are 11 nm in diameter. 6. Nucleosomes are packed when another histone (H1) associates with the linker histone, packing them into 30 nm diameter fibers. 7. These form loops held together by scaffolding proteins. 8. These interact to form the condensed chromosome seen in metaphase. E. Chromosomes of different species differ in number and information content. 1. Humans and several other species of organisms have 46 chromosomes. a) The karyotype provides a visualization of the condensed chromosomes. b) The average number of chromosomes is between 10 and 50. 2. The number of chromosomes does not provide information about the organism.
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Instructor’s Manual for Solomon, Berg, and Martin’s Biology, 9 th Edition 94 II. The cell cycle is a sequence of cell growth and division. A. Cells divide when they reach a certain size. B. Cell division (the M phase) involves mitosis and cytokinesis. 1. Mitosis involves separation of the chromosomes. 2. Cytokinesis involves division of the cytoplasm. a) Mitosis without cytokinesis results in multinucleate cells. C. Chromosomes become duplicated during interphase. 1. Cells are very active during interphase, synthesizing biological molecules and growing—the G 1 (gap) phase. 2.
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This note was uploaded on 11/17/2011 for the course BIO 101 taught by Professor Martin during the Spring '08 term at Rutgers.

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Solomon IM Ch 10 - Chapter10:Chromosomes,Mitosis,andMeiosis...

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