Genetics Practice Problems

Genetics Problems: 1) In guinea pigs black fur is dominant over white fur. How could an animal breeder epermint whether a black guinea pig is homozygous or heterozygous? 2) A short stem yellow pod pea plant is crossed with a true breeding long stem green pod pea plant. Assuming that long stems are dominant to short stems and green pods are dominant to yellow pods1) what are the genotypes and phenotypes of the F1 generation? and 2) the genotypes and phenotypes from a F1 x F1 cross? 3) In humans hemophilia (bleeder’s disease) is a recessive X-linked trait. Use a Punnett square to show the possible genotypes of offspring of a man who is a hemophiliac and a normal but heterozygous woman where XH contains the normal clotting gene and Xh contains the gene for hemophilia. 4) Lesch-Nyhan syndrome is a metabolic defect caused by the lack of the enzyme hypoxanthine-guanine phosphoribosyl transferase (HGPRT). This disease is the result of an X-linked recessive mutation and results in mental retardation selfmutilation and early death. A normal man marries a woman who had a brother who died of LNS. Your are the genetic counselor who will advise them on the likelihood of their having a LNS baby. a) What are the possible genotypes for the woman? What is the man’s genotype? b) For each of the woman’s possible genotypes what are the possible genotypes of her offspring and the implications for survival for each of them? 5) In tomatoes red fruit color is dominant to yellow. Suppose a tomato plant homozygous for red is crossed with one homozygous for yellow. Determine the phenotype and genotype of a) the F1 offspring b) the offspring of a cross of the F1 back to the red parent c) the offspring of the F1 back to the yellow parent 6) In humans the allele for free earlobes is dominant to the allele for attached earlobes. A woman with attached earlobes has children with a man who has free earlobes. a) what is the genotype of the woman? b) What is the genotype of the man? c) What proportion of their offspring will have attached earlobes? 7) Phenylketonuria (PKU) is a human autosomal genetic dis in which the affected individual cannot metabolize the amino acid phenylalanine. The disease is characterized by severe mental retardation if left untreated. The disease is caused by homozygosity for a recessive mutant allele. If two parents are heterozygous for the allele what is the probability that their child will have PKU? 8) A couple with a newborn baby is troubled that the child does not resemble either of them. Suspecting that a mix-up occurred at the hospital they check the blood type of the infant and find that it is type O. As the father is type A and the mother type B they conclude that a mix-up must have occurred. Are they correct? 9)In the fly Drosophila the allele for dumpy wings (d) is recessive to the normal longwing allele (D) and the allele for white eye (w) is recessive to the normal red-eye allele (W). In a cross of DDWW with Ddww what proportion of the offspring are expected to be “normal” (long wings and red eyes)? What proportion are expected to have dumpy wings and white eyes? 10)A farmer breeds a chicken with all white plumage with a chicken with all black plumage. All of the F1 offspring have bluish-gray plumage. When two of the bluishgray birds are crossed black white and bluish-gray offspring are produced. What is the mechanism of inheritance and the genotypes of the parents F1’s and F2’s. Requirements: 2-3 pages