Genetic Problem Questions

timer Asked: Oct 28th, 2018
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Hello there, this is a biology worksheet with questions that need to be answered. Please make sure to use tables and explain everything throughouly.

Genetics Problems 1. In a particular dog, short hair is dominant over long, and dark is dominant over light. One dog is heterozygous for hair length and shows recessive traits for hair color. Another dog is homozygous dominant for hair length and heterozygous for hair color. Identify the possible phenotypes of the offspring and give the number of each expected. 2. In fruit flies, straight wings is dominant over curly. Show how you would determine if a straight winged fly were heterozygous or homozygous? 3. In guinea pigs rough coat “R” is dominant over smooth coat “r”. Black coat “B” is dominant over white coat “b”. R and B are independent genes. Can two black coat parents produce white coat offspring? Can two white coat parents produce black coat offspring? Cross a homozygous rough black animal with a smooth white one. What will be the appearance of the F1; of the F2; of the offspring of a cross of F1 back with the rough black parent; with the smooth white parent? 4. In humans, the ability to taste phenylthiourea (PTU) is dominant. “Tasters” (TT) or (Tt) perceive an extremely bitter taste of PTU, while “non tasters” (tt) experience no sensation, or taste. a) What are the genotypes of Mr. and Mrs. Meadowmuffin, who can taste PTU, and who have 3 children, one of whom is a non‐taster? b) What offspring phenotypes would be expected from the following crosses and in what ratio? i) heterozygous x heterozygous ii) homozygous taster x heterozygous iii) heterozygous x non taster 5. A plant of genotype TTYy was crossed with one of genotype ttYy. If the cross yielded 800 seeds, what number of what phenotypes probably resulted? What were their genotypes? 6. A dominant gene (S) in snapdragons produces bilaterally symmetrical (“irregular”) flowers; the recessive allele (s) produces radically symmetrical flowers. Another pair of alleles controls color, yielding red (A1A1), pink (A1A2), or white (A2A2). If a cross is made between two snapdragons of genotype SsA1A2, what will be the phenotypes of F1? Give the proportions of each. 7. Two fruit flies with normal wings are crossed. Among 123 offspring, 88 have normal wings and 35 have curly wings. What inheritance pattern is shown by the normal and curly alleles? What were the genotypes of the two parents? 8. Flower color in certain plants is governed by epistasis. P= purple p= white, C= curved petals, c= straight petals. A homozygous recessive petal shape prevents purple color. If parent plants are Ppcc x PPCc, what is the genotypic and phenotypic ratios of the offspring? 9. Assume that straight hair allele is recessive. The dominant allele gives curly hair. Two curly haired parents have a straight haired child. a) b) c) d) What are the genotypes of the parents? What is the genotype of the child? Give two genotypes for curly haired people. Using letter symbols show two different crosses for a curly haired individual crossed with straight haired individual. 10. In pigeons, the checkered pattern results from the dominant gene C and plain coloration on the recessive gene c. Red color is controlled by a dominant gene R and by the brown recessive gene. a) A homozygous checkered, red bird and a plain, brown bird are crossed. Summarize the expected F1 and F2 results, giving both genotype and phenotype. b) Male checkered, red birds with the genotype CcRr were mated with females of the following genotypes: (i)CCRR (ii)Ccrr (iii)ccrr. Summarize the expected first generation results of each cross, giving all ratios. 11. A rooster with grey feathers is mated with a hen of the same phenotype. Among their offspring, 15 chicks are grey, 6 are black, and 8 are white. What is the simplest explanation for the inheritance of color in the chicks? What offspring would you expect from the mating of a grey rooster and a black hen? 12. A black guinea pig crossed with an albino guinea pig produces 12 black offspring. When the albino was crossed with a second black one, 7 blacks and 5 albinos resulted. What is the best explanation for these results? Give genotypes for parents and all offspring. 13. The allele that causes albinism (p) is recessive to the allele for normal pigmentation (P). A normal woman whose father is an albino marries an albino man whose parents are both normal. They have three children, two normal, and one albino. Give the genotype for each individual. 14. If a color‐blind male marries a carrier female, what are the chances that their sons will be color blind? What are the chances that their daughters will be carriers? 15. A color‐blind man and a woman with normal vision whose father was color blind have a son. What is the probability that they will have a color‐blind daughter? 16. Hemophilia is an X‐linked recessive trait. A woman who is seemingly normal but whose father was a hemophiliac marries a normal man. What proportion of their sons will have hemophilia? Their daughters? What proportions of their daughters will be carriers? If the couple has four sons, what is the probability that all four will be born with hemophilia. 17. a) If a carrier female marries a normal male, what are the chances of their offspring having the disease hemophilia? What are the chances of their sons being normal? What are the chances of their daughters being a carrier? b) If a woman’s father had hemophilia, what are the chances that she is normal? If her mother was a carrier, what are the chances that she is normal? A carrier?

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