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Homework Help: Can anyone help me with ny of these 4 genetics questions?

  1. Sep 22, 2007 #1
    1. The genes for mohogany eyes and ebony body are approximately 25 map units apart on chromosome III in Drosophila. Assume that a mahogany-eyed female was mated to an ebony-bodied male and the resulting F1 phenotypically wild type females were mated to mahogany, ebony males. Of 1000 offspring, what would be the expected phenotypes and in what numbers would they be expected?

    2. Given that loci A and B in Drosophila are sex-linked and 20 map units apart, what phenotypic frequencies would you expect in male and female offspring resulting from the following crosses? (Assume A and B are dominant to a and b, respectively):
    (a) AaBb(cis)female X ab/Y male
    (b) AaBb(trans) X ab/Y male
    (c) aabb female X AB/Y male

    3. Assume that there are 12 map units between two loci in the mouse and that you are able to microscopically observe meiotic chromosomes in this organism. If you examined 200 primary oocytes, in how many would you expect to see a chiasma between the two loci mentioned above?
    I got 2 for an answer. Is that correct?

    4. Phenotypically wild F1 female Drosophila, whose mothers had light eyes(Lt) and fathers had straw(stw) bristles produced the following offspring when crossed to homozygous light-straw males:
    phenotype: number:
    light-straw 22
    wild 18
    light 990
    straw 970
    total: 2000
    Compute the map distance between light and straw loci.
    I got 1.1 mu for an answer. Is that correct?

    Thanks in advance for any help.
  2. jcsd
  3. Sep 26, 2007 #2


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