Name: # Date: Per: Genetics Extra Practice Show all work! Monohybrids 1. A cross between two pea plants hybird for a single trait produces 60 offspring. Approximately how many of the offspring would be expected to exhibit the recessive trait? 2. Polydactyly is a human characteristic in which a person has six fingers per hand. The trait for polydactyly is dominant over the trait for five fingers. If a man who is heterozygous for this trait marries a woman with the normal number of fingers, what are the chances that their first child would be polydactyl? 3. In guinea pigs, black coat color is dominant over white coat color. Show the genotypic and phenotypic ratios of the offspring of a mating between two heterozygous black guinea pigs. 4. If a breeder wanted to discover whether a black guinea pig was homozygous (BB) or heterozygous for coat color, the animal in question would be crossed with what kind of individual? Explain the cross and the possible results.
Dihybrids 1. In cats, the allele for black fur is dominant to the allele for brown fur, and the allele for short hair is dominant to the allele for long hair. Show the geneotype ratios and corresponding phenotype ratios of the following crosses: a. a diheterozygous male with a heterozygous black fur long hair female b. a homozygous black fur heterozygous short hair male, heterozygous black fur long hair female c. a diheterozygous male with a dihomozygous recessive female
2. In tomato plants, the allele for purple stems is dominant to allele for green stems and the allele for red fruit is dominant to the allele for yellow fruit. If two tomato plants heterozygous for both traits are crossed, show the punnet square. State what proportion of the offspring would be expected to have: a. purple stems and yellow fruit: b. green stems and red fruit: c. purple stems and red fruit: 3. If 640 seeds resulting from the cross above are collected and planted, determine how many are expected to grow into plants with: (don t forget to show work!) a. red fruit b. green stems c. both yellow fruit and green stems Incomplete and Codominance 1. When a mouse with black fur is crossed with a mouse with white fur, all F1 generation offspring have gray fur. What genotypic and phenotypic ratios be expected in the F2?
2. In cattle hair color shows codominance. Red is dominant, and white is recessive. In the heterozygous condition codominance is shown as a roan coat color. If a roan bull and a roan cow are mated over several years and produce 12 offspring. How many of the offspring would be expected to be white? Roan? Pedigrees 1. Write the genotypes for each of the following individuals (hint: autosomal recessive) Sex-linked 1. If a man with hemophilia (difficulties with blood clotting) marries a homozygous normal woman, what is the probability of them having a hemophiliac child? 2. Optic atrophy (blindness due to degeneration of the optic nerve) occurs as a result of the action of an X-linked recessive gene. A woman with optic atrophy marries a normal man. What is the expected genotypic and phenotypic ratio of their children?
Multiple Alleles 1. Give the genotypic and phenotypic ratio of the potential children of a couple, if the man is heterozygous A-type blood and his wife is heterozygous B-type blood. 2. A test was done to determine the biological father of a child. The child's blood Type is A and the mother's is B. Dude #1 has a blood type of O, & dude #2 has blood type AB. Which dude is the biological father? 3. What are the chances of a woman with Type AB and a man with Type A having a child with Type O? One More! 1. A man that has hemophilia marries a woman who is a carrier. They have 4 children; a son who dies of hemophilia, 1 carrier daughters and 2 normal sons. The carrier daughter marries a normal man and has 3 children; 2 normal boys and 1 boy with hemophilia. Explain the possible outcomes if the son with hemophilia has a daughter.