linkage+question+from+lecture - relationships CAN’T be...

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A) Given: A certain type of dog does not undergo recombination, and has three simple Mendelian genes that control the curliness, color, and length of its coat. If you cross white, straight-haired dogs with true breeding black, curly- haired dogs, the progeny are always black, curly-haired. When dogs with curly, white, short hair mate with a dogs with straight, black, long hair, puppies with four kinds of coat emerge, in equal proportions: curly, black and long curly, white and long straight, black and long straight, white and long 1. Which alleles are dominant, which are recessive? Because straight white dogs crossed with true breeding curly black dogs only yield curly black puppies, one can infer that Curly and Black are dominant. Due to the emergence of only long-haired puppies, Long is also dominant. 2. What are the genotypes of the parents? The offspring? Parents: Cc bb ll and cc Bb LL. Offspring: Cc Bb Ll, Cc bb Ll, cc Bb Ll, and cc bb Ll. 3. What linkage relationships can you determine from this information? What
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Unformatted text preview: relationships CAN’T be determined? Why? You cannot establish ANY linkage relationships, because each parent is only heterozygous at one locus. To establish linkage between two loci, ONE parent must be heterozygous at BOTH loci – otherwise, you can’t tell if the alleles are segregating independently or not. 4. To further test the linkage relationships of these genes, what cross should you do next? The next cross would be Cc Bb Ll X cc bb ll. B) You take a curly, black, long-haired dog from the previous mating, and cross it with a straight, white, short-haired dog. Puppies emerge in the following proportions: curly, black and short - 25% curly, white and short - 25% straight, black and long - 25% straight, white and long - 25% What are the linkage relationships between the genes? C is linked to L, in repulsion. The original parents: Cl/cl; b/b X cL/cL; B/b F1 cross: Cl/cL; B/b X cl/cl; b/b....
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This note was uploaded on 10/27/2009 for the course BIO SCI 05580 taught by Professor Marsh during the Fall '09 term at UC Irvine.

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