Lecture 5 Bio325 Fall 07

Lecture 5 Bio325 Fall 07 - CHROMOSOMES single molecules of...

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1 CHROMOSOMES : single molecules of DNA (double-stranded) that carry the information that determines hereditary traits initial validation of the chromosomal basis of inheritance came from microscopy- based experiments in cells from insects, frogs, and sea urchins chromosomes condense prior to cell division; during this time they can be visualized as discrete entities, shown here in this human karyotype most cells in the human body are diploid : containing two matching sets of chromosomes; these are the somatic cells. Sperm from males and oocytes from females are haploid : containing only one set of chromosomes; these are the germ cells (gametes) The difference in size between the X and Y chromosomes was critical for the validation of the chromosomal theory of inheritance Fig. 4.3 identical not identical Are homologous chromosomes identical? homologous chromosomes look identical in a microscope, and usually contain all the same genes, but at the sequence level they are not identical, unless the parents of the individual were related.
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2 The cell cycle: alternating cycles of chromosomal replication and cell division Fig. 4.7 Fig. 4.8
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3 mitosis meiosis meiosis fertilization 2n 2n 2n 2n 2n 2n 2n 2n 2n 2n 2n 2n 2n 2n 2n 1n 2n 2n 2n 1n 1n 2n 2n 2n 2n 2n 2n 2n 1n 2n 2n 2n 2n 2n 2n 2n 2n 2n 2n 2n 2n 2n mitosis Typical life cycle of a sexual multi-cellular organism: 2n Sexual reproduction: characterized by alternating cycles of meiosis and fertilization: Reproduction that takes place through the combination of gametes , to form a new individual
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This note was uploaded on 06/19/2008 for the course BIO 325 taught by Professor Saxena during the Fall '08 term at University of Texas.

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Lecture 5 Bio325 Fall 07 - CHROMOSOMES single molecules of...

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