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College of Cat Genetics: Part II
by Patricia Turner


  1. In the cat there are thirtysix autosomes in addition to the two X chromosomes in the female and one X and one Y in the male.  What are the chromosome constitutions of the two types of gamete produced by the male?



    Answer: The chromosome complement of the two types of gamete produced by the male cat are (a) 36 autosomes plus two X chromosomes, and (b) 36 autosomes, one X chromosome and one Y chromosome.  (a) gametes will be female and (b) gametes will be male.

  3. Why do genetic differences between cells arise from meiosis and not from mitosis?



    Answer:  Genetic differences arise during meiosis rather than from mitosis because mitosis is the normal type of cell division in which the cells divide in a manner resulting in all the daughter cells retaining the full complement of 38 chromosomes.  But in the cell division that occurs just before the gametes are formed (meiosis) each daughter cell has only 19 chromosomes.  It is only at fertilization, when the daughter cells from each partner unite, that the full complement of 38 is regained.  Clearly the fertilized cells will have some chromosomes from each parent and will differ from those produced by each parent during mitosis.  Mitosis results in daughter cells with the same chromosome complement whereas meisosis results in daughter cells with half the chromosome complement.

  5. Recessive Oregon Rex, recessive Cornish Rex and recessive Devon Rex are non-allelic to each other.  Will a mating between an Oregon Rex queen and either a Cornish OR Devon Rex stud produce any rex kittens?  If the litter includes any non-rex kittens, will they be carriers for the rex varieties of both parents or only of one?



    Answer:  No, a mating between an Oregon Rex queen and either a Cornish or a Devon Rex queen will not produce any rex kittens.  They will all have normal hair.  The non-rex kittens will be carriers for both Rex varieties as the three varieties of rex are non-allelic to each other.

  7. In a litter from a Seal Tabby (or Seal Lynx) Point Siamese there are three Seal Point kittens and one Seal Tabby (or Lynx) Point kitten.  Is the Tabby (Lynx) point homozygous or heterozygous for agouti and will the Seal Point kittens later produce Tabby (Lynx) Point progeny if mated to Seal Points?



    Answer:  The Tabby (or Lynx) Point kitten is heterozygous for agouti.  The Seal Point kitten will never produce Tabby (or Lynx) Points if mated to Seal Points.