genetics - Introduction to Genetics Reading: Freeman,...

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Introduction to Genetics Reading: Freeman, Chapter 13, also Chapter 12
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Information Every living thing is organized via coded information, called its genetic material . Reproduction involves duplication and transmission of an organisms genetic material
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Prokaryotes , which include cyanobacteria, archaeans, and bacteria, are the simplest, oldest, and most common organisms on the planet. Prokaryotes have simple loops of DNA (with associated proteins). This loop is attached to the cell membrane. ....Even though the structure simple, there is a lot of DNA in a single bacterium. .… Stretched out, the DNA in an E. coli would be 500 times longer than the cell itself.
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In prokaryotes, the DNA loop replicates before fission, with both loops still attached to the cell membrane ....During fission, as the cell membrane splits in two, one loop of DNA ends up in each new “daughter cell”
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Eukaryotes , which include ciliates, amebas, fungi, plants, animals, etc., have linear strands of DNA arranged in structures called chromosomes and packed into a nucleus (or nuclei, in some cases). Most eukaryotes have enormously more DNA than prokaryotes, tens to millions of times more. These strands are enormously long, and extended (thus, invisible to microscopes) during the normal life of the cell.
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The increased amount of DNA necessitates a means of condensing these long strands into compact structures that can be sorted into separate daughter cells. Histones : loops of DNA are wrapped around one histone (like thread around a spool), and locked in by a second, forming a structure called a nucleosome .
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Sexual Reproduction Formation of new individual by a combination of two haploid sex cells (gametes). Fertilization- combination of genetic information from two separate cells that have one half the original genetic information. Fertilization enables a tremendous variety of new diploid genotypes to be formed. Gametes for fertilization usually come from separate parents: female produces an egg and male produces sperm. Both gametes are haploid, the resulting zygote is diploid.
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Diploid-Haploid Diploid organisms have two complimentary sets of chromosomes ( homologous chromosomes). Each chromosome has exactly the same genes in the same sequence, as its compliment (except in the case of a deletion), although they will frequently have different alleles , or versions of these genes. Meiosis starts with a single diploid cell with two redundant sets of DNA, and produces four haploid cells, each with a single set of DNA- these four cells all have DIFFERENT sets of alleles, although they have the same genes.
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Meiosis Meiosis is essential for sexual reproduction. It is also the cytological basis of Mendelian genetics.
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This note was uploaded on 04/02/2009 for the course CHEM 112 taught by Professor Jursich during the Spring '08 term at Ill. Chicago.

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genetics - Introduction to Genetics Reading: Freeman,...

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