BIOL 101 1nd Edition Lecture 15 Outline of Last Lecture I Law of Equal Segregation II Alleles III Single Gene Crosses Outline of Current Lecture I Application II Pedigrees III Problems involving Pedigrees Current Lecture Thinking like a geneticist and applying what you know In fruit flies a mutation leads to small wings Is this dominant or recessive How can you find out The cross that you might do A purebreeding fruit fly with small wings was crossed to a purebreeding fruit fly with normal wings and all the progeny had small wings When the F1 generation was interbred 400 F2 flies were counted 305 had small wings and 95 had wild type wings Which allele is dominant small Write the genotypes of the F1 flies Write the genotypes of the F2 flies Aa small wings A wild wings AA small wings Aa small wings aa wild wings In this example the mutant allele is not recessive to the wildtype allele The wildtype allele is NOT always the dominant allele I Pedigrees allow us to determine the pattern of inheritance of a familial disorder i Recessive Disorders These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Skip generations the colored in ones are the affected Children with unaffected parents can be affected ii Dominant Disorders Present in every generation 1 Is the genetic disorder represented in the pedigree to the right recessive or dominant Hint Think about how we defined these terms 2 How do you know It skips generations and child with disorder is born to unaffected parents What are the probable genotypes of various individuals in the pedigree For example what is the genotype of I 2 II 4 Important assumption the disease allele is rare in the population so people marrying into the family are assumed to not have the disease allele II The rule of multiplication can be used to determine the probability that a child has a rare genetic disorder i Rule of multiplication the probability that two independent events will occur is the product of their individual probabilities PRACTICE Determine the probability that if individuals III 1 and III 2 marry their child will have the autosomal recessive disease represented in this pedigree Aa Aa aa AA or Aa Aa or AA AA AA Aa or AA Aa or AA AA or Aa Aa Aa or AA Aa aa Approaching the problem 1 Calculate the probability that the unborn child s father carries the disease allele probability that the unborn child s grandfather is a carrier 2 3 x probability that the unborn child s father is a carrier 1 2 1 3 2 Calculate the probability that the unborn child s mother carries the disease allele probability that the unborn child s grandmother is a carrier 1 x probability that the unborn child s mother is a carrier 1 1 3 The probability that if III 1 and III 2 marry their child will have the autosomal recessive disorder 1 4 probability that the father will carry the disease allele 1 3 x probability that the mother will carry the disease allele 1 x probability that the unborn child will have the disease 1 4 Drum roll please THE ANSWER 1 12
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