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Unformatted text preview: Sex Determination in Drosophila Drosophila has 4 pairs of chromosomes (n=4, 2n=8). The X and Y chromosomes are counted as chromosome #1, and then there are 3 other autosomes (2, 3, and 4). The diagram below is from a female Drosophila, so there are 2 X chromosomes. In the above diagram, there are 2 of each of the autosomes (2 chromosome #2s, 2 chromosome #3s, and 2 chromosome #4s). This gives the 2A part of the ratio when determining sex. Each autossomal set consists of a chromosome 2, 3, and 4 together. Normal diploid Drosophila cells are diploid, so they have 2 sets of autosomes. Sometimes, cells can be haploid (just one set of autosomes), with just one of each chromosome. In that case, A=1. Sometimes, the cells can be triploid, with 3 sets of autosomes, A=3. To determine the sex of the individual, just determine how many sets of autosomes are present (all diagrams here have 2 sets), and how many X chromosomes are present, then take the X:A ratio to determine the sex according to the information from your notes and your text. ...
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This note was uploaded on 09/12/2008 for the course BICD 100 taught by Professor Nehring during the Spring '08 term at UCSD.
 Spring '08
 Nehring
 Genetics

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