advgene - Biol 215 Advanced Genetics Advanced Genetics Gene...

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Advanced Genetics Advanced Genetics Gene Mapping 1 The recessive gene s produces shrunken endosperm in corn kernals and its dominant allele S produces full, plump kernals. The recessive gene c produces colorless endosperm and its dominant allele C produces colored endosperm. Two homozygous plants are crossed, producing an F1 which are all phenotypically plump and colored. The F1 plants are test-crossed with homozygous recessive plants and produce the following progeny: shrunken, colorless 4035 plump, colored 4032 shrunken, colored 149 plump, colorless 152 a) What were the phenotypes and genotypes of the original parents? b) How are the genes linked in the F 1 ? c) Calculate the map distance between the two gene loci. 2. In corn, the gene R for red color is dominant over the gene r for green color. The gene N for normal seeds is dominant over the gene n for tassel seed. A fully heterozygous red plant with normal seeds was crossed with a green plant with tassel seeds, and the following ratios were obtained in the offspring: 124 red, normal 77 red, tassel 126 green, tassel 72 green, normal. Does this indicate linkage? If so, what is the map distance between the two loci? 3. Suppose genes A and B are 14.5 map units apart. Another gene, C, linked to these, is found to cross with gene B, 7 percent of the time. Are these data sufficient to determine the exact order of the three genes? If not, what other information is needed to order the genes? 4. The cross-over percentage between linked genes J and M is 20%, J and L 35%, J and N 70%, L and K 15%. M and N 50%, M and K 30%, and M and L 15%. Thus , the sequence of genes on this chromosome is ______________________________________________________ 5. One of your unicorns gives birth after you and she toured the Ukraine. The does not look like its parents or your other unicorns. While your animals have a straight horn and a green coat; this one has a twisted horn and a blue coat. You mate “Old Blue” and keep only the blue offspring, after successive generations you have pure- breeding progeny of “Old Blue." Now when you mate animals from your two populations: all the progeny have straight horns and green coats. These hybrid offspring are then crossed to unicorns with twisted horns—blue coats. This cross produces offspring in the following numbers:
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advgene - Biol 215 Advanced Genetics Advanced Genetics Gene...

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