Problem 13 imagine that a newly discovered

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Problem 13
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Imagine that a newly discovered, recessively inherited disease is expressed only in individuals with type O blood, although the disease and blood group are independently inherited. A normal man with type A blood and a normal woman with type B blood have already had one child with the disease. The woman is now pregnant for a second time. What is the probability that the second child will also have the disease? Assume both parents are heterozygous for the "disease" gene. Genotype Father AO Mother BO OO expresses the disease The second child’s chance of having the disease is = x = 1/16 Problem 14 In tigers, a recessive allele causes an absence of fur pigmentation (a "white tiger") and a cross-eyed condition. If two phenotypically normal tigers that are heterozygous at this locus are mated, what percentage of their offspring will be cross-eyed? What percentage will be white?
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Using the Punnett square below where P = normal pigmenation and p = white then 25% will be white (pp) and all of the white offspring will also be cross-eyed Problem 15 In corn plants, a dominant allele I inhibits kernel color, while the recessive allele i permits color when homozygous. At a different locus, the dominant gene P causes purple kernel color, while the homozygous recessive genotype pp causes red kernels. If plants heterozygous at both loci are crossed, what will be the phenotypic ratio of the F1 generation? Phenotypic ratios: White (I _ _ _) = 12 Purple (i i P_ ) = 3
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Red ( i i p p) = 1 The dominant allele I is epistatic to the p locus, and thus the F1 generation will be: 9 I_P_ : colorless 3 I_pp : colorless 3 i iP_ : purple 1 i i pp: red Problem 16 The pedigree below traces the inheritance of alkaptonuria, a biochemical disorder. Affected individuals, indicated here by the filled-in circles and squares, are unable to break down a substance called alkapton, which colors the urine and stains body tissues. Does alkaptonuria appear to be caused by a dominant or recessive allele? Recessive Fill in the genotypes of the individuals whose genotypes you know. What genotypes are possible for each of the other individuals? If alkaptonuria is recessive George must be a carrier. See below.
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If alkaptonuria is dominant Carla could not have the disease, as indicated in the pedigree chart, since the parents do not express the trait. See Below. Problem 17 A man has six fingers on each hand and six toes on each foot. His wife and their daughter have the normal number of digits (5). Extra digits is a dominant trait. What fraction of this couple’s children would be expected to have extra digits?
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Because the daughter is normal the man’s genotype must be heterozygous for the trait so: if X = extra digits and x = normal (5) digits then: 50% of the offspring will be polydactylic Problem 18 Imagine you are a genetic counselor, and a couple planning to start a family came to you for information. Charles was married once before, and he and his first wife had a child who has cystic fibrosis.
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  • Spring '14
  • Callos,ChristinaT
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