P X p2 Y x X p3 X p3 X p3 Y x X p3 X p2 X p3 Y X p2 Y X p3 X p3 X p3 X p2 2 pr

P x p2 y x x p3 x p3 x p3 y x x p3 x p2 x p3 y x p2 y

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P X p2 Y x X p3 X p3 X p3 Y x X p3 X p2 X p3 Y X p2 Y X p3 X p3 X p3 X p2 2-pr M F 3-pr M F 3-pr M 2-prM F F c) Show the F1 and F2 of the reciprocal cross for part b). P X p3 Y x X p2 X p2 X p2 Y x X p3 X p2 X p3 Y X p2 Y X p2 X p2 X p3 X p2 2-pr M F 3-pr M F 3-pr M 2-prM F F d) Make a comment on which allele is dominant and give a good reason for your answer. In order to tell which allele is dominant, you have to look at the heterozygote. In this case the heterozygote is female and does not have antlers. The male is hemizygous and does not have two alleles for this trait. Thus, in this case it cannot be determined which allele is dominant. 7. A variety of squash has fruits that weigh about 3kg. In a second variety the average weight is 1kg. When the two varieties are crossed, the F1 produce fruit with an average weight of 2 kg. When F1 plants are crossed, a range of fruit weights is found, from 1 to 3 kg. Of two hundred offspring, three produce fruits weighing about 3 kg and three produce fruits about 1 kg in weight. a) How many allelic pairs are involved in the weight difference between the varieties and approximately how much does each allele contribute to the difference? 3 in 200 is approximately 1/64 = (¼) 3 therefore there are three loci. Thus there are 6 contributing alleles. Each effective allele contributes about 1/3kg over the 1kg base (2 kg difference divided by 6 effective alleles). b) Suggest genotypes for each original plant and the F1. 3 kg plant = AA BB CC 1kg plant = aa bb cc F1 = Aa Bb Cc 8. Assume that height in people depends on four pairs of alleles. How can two persons of moderate height produce children who are much toller than they are? Assume that the environment is exerting a negligible effect. This would come about by independent assortment. Parents (with 4 contributing alleles) who are Aa Bb Cc Dd could produce children with 5 or more contributing alleles ie, Aa BB, CC, dd or AA BB CC DD or Aa BB CC DD
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9. Variations in stature are almost entirely due to heredity. Yet average height has increased substantially since the Middle Ages, and the increase in height of children of immigrants to North America, as compared with height of the immigrants themselves, is especially noteworthy. How can these differenced be explained? Improved nutrition, medicine and sanitation affect almost all people, allowing genetic potential to be universally affected. Thus variation in a population can be genetic, whereas the mean value can be under the control of the environment. In other words, impoverished people have genetic variation about a low mean, whereas well-fed people have genetic variation about a high mean.
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  • Spring '11
  • dr
  • Genetics, 2m, VE, heterozygote, 20g

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