Genetics Practice Mendelian Problems Short - Practice...

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Practice Problems in Mendelian GeneticsImportant Note: Get in the habit right from the first of writing down the work necessary to solve the problems you do.You will be required to show work on any assignment or exam problem.I.Problems Involving One Gene1.In cats, long hair is recessive to short hair. A true-breeding (homozygous) short-haired male is matedto a long-haired female. What will their kittens look like?2.Two cats are mated. One of the parent cats is long-haired (recessive allele). The litter which resultscontains two short-haired and three long-haired kittens. What does the second parent look like, andwhat is its genotype?3.Mrs. And Mr. Smith both have widow’s peaks (dominant). Their first child also has a widow’s peak, buttheir second child doesn’t. Mr. Smith accuses Mrs. Smith of being unfaithful to him. Is he necessarilyjustified? Why or why not? Work the genetics problem predicting the frequencies of the versions ofthis trait among their prospective children.4.Mr. and Mrs. Jones have six children. Three of them have attached earlobes (recessive) like theirfather, and the other three have free earlobes like their mother. What are the genotypes of Mr. andMrs. Jones and of their numerous offspring?5.Mr. and Mrs. Anderson both have tightly curled hair. (The hair form gene shows incompletedominance. There are two alleles, curly and straight. The heterozygote has wavy hair.) The Andersonshave a child with wavy hair. Mr. Anderson accuses Mrs. Anderson of being unfaithful to him. Is henecessarily justified? Why or why not?6.Two wavy haired people (one male and one female) marry and have eight children. Of these eight, howmany would you expect to be curly haired, how many wavy haired and how many straight haired,assuming that the family follows the expected statistically predicted pattern? Suppose you examinethe actual children and discover that three of the eight have curly hair. What do you suppose wentwrong?7.Basic body color for horses is influenced by several genes, on of which has several different alleles.Two of these allelesthe chestnut (dark brown) allele and a diluting (pale cream) allele (oftenincorrectly called ‘albino’)—display incomplete dominance. A horse heterozygous for these two allelesis a palomino (golden body color with flaxen mane and tail). Is it possible to produce a herd of pure-breeding palomino horses? Why or why not? Work the Punnett’s square for mating a palomino to apalomino and predict the phenotypic ratio among their offspring.8.In certain portions of the Jewish population, there is a genetic disease called Tay Sachs disease,which is fatal to infants within the first five years of life. This disease is caused by a recessive alleleof a single gene. Why does this disease persist, even though it isinvariablyfatal long before theafflicted individual reaches reproductive age? (In other words, why doesn’t the allele for Tay Sachsdisease simply disappear?)

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