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Homework Help: Mendelian explanation for bicolor coated puppy

  1. Aug 18, 2014 #1
    1. Mendelian experiments only explain dominant vs recessive gene ratios after generations created by assorted types of mating. But how can I explain the puppy's bicolor coat of black and white given that its parents are one black and one white

    2. Supposing that W and B are dominant genes of white and black colors and so 'w' and 'b' are recessive ones. What is the puppy's with a dotted coat ?

    3. The attempt at a solution. I wish to but truly I don't know
  2. jcsd
  3. Aug 23, 2014 #2


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    The word for it is 'mosaicism'. It happens when different genes of the diploid genome are expressed in different cells and their cellular descendants. It happens most famously with X chromosomes in females. One of the X chromosomes in the XX cells has to be inactivated as otherwise the cell gets an overdose, since one X works in males so that is the right dosage for these genes. The X chromosome inactivation happens by DNA methylation. But it happens some way along the developmental pathway e.g. When there are a dozen or two precursors of the pigment-producing cells, and happens randomly so in some cells one chromosome is inactivated and go on to produce one fur colour, in others the other. Although female's tissues are mosaic for all X-chromosome products, in most cases this would not produce any such obviously noticeable phenotypic effect.

    The most well known case is very similar to your example - tortoiseshell cats.

    There are other mosaicism mechanisms though.

    Follow up with google the various bolded keyphrases.
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