Genetics worksheet Hochs answers 11-13-19

Genetics Worksheet Name: _______________________ A fly species has two alleles for wing shape: Curly (C) and flat (c). The Curly (C) allele exhibits dominance and the flat allele is recessive to it. What possible sperm would be produced by a HETEROZYGOUS male? C or c What eggs would be produced by a female with flat wings? Only c Use the Punnett Square to predict the genotype ratio and phenotype ratios of offspring Father’s Contribution C c Mother’s Contribution c Cc cc c Cc cc Genotype ratio: 1:1 (reduced from 2:2) Phenotype ratio: 1:1 (reduced from 2:2) A plant species has two alleles for stem length: Long (L) and Short (l). The Long (L) allele exhibits incomplete dominance. The intermediate phenotype is intermediate stems. Imagine that a male plant with intermediate stems pollinates a female plant with intermediate stems. What sperm and ova are produced by each? Both produce L and l Use the Punnett Square to predict the genotype ratio and phenotype ratios of offspring Father’s Contribution L l Mother’s Contribution L LL Ll l Ll ll Genotype ratio: 1:2:1 (homozygous dominant: heterozygous: homozygous recessive) Phenotype ratio: 1:2:1 (Long: Intermediate: short) In some mice, fur color can be agouti or yellow. Agouti (y) is recessive to yellow (Y), however those offspring that are homozygous for the yellow gene do not advance past the zygote stage, instead those embryos miscarry. Imagine that two yellow mice that are both heterozygous mate with each other. What color are the two mating mice? YELLOW What sperm and ova are produced by each? Y and y Use the Punnett Square to predict the genotype ratio and phenotype ratios of offspring Father’s Contribution Y y Mother’s Contribution Y YY Yy y Yy yy Genotype ratio: 1:2:1 (homozygous dominant: heterozygous: homozygous recessive) Would be seen as 2:1 after birth because the YY individuals miscarry Phenotype ratio: 1:2:1 (agouti:yellow:dead) Would be seen as 2:1 after birth because YY individuals miscarry) Why might this type of genetic cross been confusing to those studying mice genetics for the first time? Odd ratios because 25 percent of embryos are not born Now use the Punnett Square to predict the genotype ratio and phenotype ratios of offspring of a yellow mouse dad and an agouti mouse mom Father’s Contribution Y y Mother’s Contribution y Yy yy y Yy yy Genotype ratio: 1:1 (reduced from 2:2, Heterozygous : homozygous recessive). Phenotype ratio: 1:1 (reduced from 2:2, yellow : agouti). In blood typing, type A and type B follow a pattern of codominance. Homozygotes have whatever bloodtype they are homozygous for, and heterozygotes or A and B have AB blood, with both antigens. Type A and Type B are both Dominant to Type O. Heterozygotes that have an O allele express the dominant gene’s blood type. Those homozygous for O have O blood. Suppose a father of blood type A and a mother of blood type B have a child of type O. Can you deduce the genotypes of the parents? Since both passed an O allele to child (the only genotype generating type O phenotype is OO), they must be AO and BO What blood types are possible for the other children of this couple? AB, A (genotype AO), B (genotype BO) and O (genotype OO) Imagine we gather 1000 children whose parents both all Type AB blood. Predict the number of those children with type B blood. 250 (1000 time 25%) Perform a Punnett Square of a cross between a male and female human, demonstrating that there is a 50% chance of having a son (genotype XY) and a 50% chance of having a daughter (genotype XX). Father’s Contribution X Y Mother’s Contribution X XX XY x XX XY Explain why it is impossible to ever have a child with a YY genotype for sex chromosomes. Mothers never have a Y, so they can’t pass it on. Also, cannot survive without at least one X chromosome. The genes for color vision are found on the X Chromosome. That means females are all diploid for their color vision genes, but males are haploid. If a male has a defective color vision gene (Xcb), his genotype is (XcbY) and he is colorblind. If a female has one defective color vision gene, her genotype is (XcXcb) and she usually has normal color vision. Females with (XcbXcb) are colorblind. Perform a Punnett square for a couple where the female is homozygous for normal color genes (XcXc) and the male is colorblind (XcbY) Father’s Contribution Xcb Y Mother’s Contribution Xc Xc Xcb Xc Y Xc Xc Xcb Xc Y What is the sex ratio of potential offspring? It is ½ male to ½ female. Are any of the offspring colorblind? There are no colorblind children because there are no females with Xcb Xcb and no males with Xcb Y. Let us imagine a family in which the father is colorblind and the mother is a carrier for the color blind gene. Father’s Contribution Xcb Y Mother’s Contribution Xcb Xcb Xcb Xcb Y Xc Xcb Xc Xc Y What is the sex ratio of potential offspring? The ratio is ½ male to ½ female. Are any of the offspring colorblind? Yes, 50% of the offspring are colorblind. One female of four possible offspring is colorblind while one male offspring is colorblind. Why are there so many more color blind men than women? More men are colorblind than women because for the male sex genotype there is only one X. If the males inherit the effected X then they will express colorblindness. The female sex genotype is XX, if they inherit one effected X then the non-effected X will be expressed and not the effected colorblind carrying X. Due to the fact that males only have one X, if the X they inherit expresses colorblindness than it will affect the offspring. Identify your phenotype and the phenotype of both your parents for as many of the following traits as you can: Ability to roll tongue is Dominant. Homozygous recessive cannot roll tongue. Widow’s peak is Dominant. Homozygous recessive has a straight hairline. Free earlobes are Dominant. Homozygous recessive has attached earlobes. Straight thumbs are Dominant. Homozygous recessive has bent back thumbs, the “hitchhiker thumb”/ Give your phenotype and that of your parents, can you deduce your GENOTYPE? Do this for blood type too, if you have this information. A pea plant is heterozygous for both seed shape and seed color. S is the allele for the dominant, spherical shape characteristic; s is the allele for the recessive, wrinkled shape characteristic. Y is the allele for the dominant, yellow color characteristic; y is the allele for the recessive, green color characteristic. A plant breeds true round, yellow peas. What is its genotype? What pollen will it produce? SY only. True breeding means it is homozygous for those traits Another plant breeds true for wrinkly, green peas. What is its genotype? What ova will it produce? sy only. True breeding means it is homozygous for those traits Use the Punnett Square to predict genotypes and phenotypes of offspring SY SY SY SY sy Genotype: SsYy Phenotype: Round and yellow Genotype: SsYy Phenotype: Round and yellow Genotype: SsYy Phenotype: Round and yellow Genotype: SsYy Phenotype: Round and yellow sy Genotype: SsYy Phenotype: Round and yellow Genotype: SsYy Phenotype: Round and yellow Genotype: SsYy Phenotype: Round and yellow Genotype: SsYy Phenotype: Round and yellow sy Genotype: SsYy Phenotype: Round and yellow Genotype: SsYy Phenotype: Round and yellow Genotype: SsYy Phenotype: Round and yellow Genotype: SsYy Phenotype: Round and yellow sy Genotype: SsYy Phenotype: Round and yellow Genotype: SsYy Phenotype: Round and yellow Genotype: SsYy Phenotype: Round and yellow Genotype: SsYy Phenotype: Round and yellow What is the phenotype ratio? 100% round and yellow Imagine we breed a plant that is homozygous for both the wrinkly pea gene and green pea gene with a plant that is heterozygous for both genes. Using the information from the previous page, make the Punnett square showing this cross: sy sy sy sy SY Genotype: SsYy Phenotype: Round and yellow Genotype: SsYy Phenotype: Round and yellow Genotype: SsYy Phenotype: Round and yellow Genotype: SsYy Phenotype: Round and yellow Sy Genotype: Ssyy Phenotype: round and green Genotype: Ssyy Phenotype: round and green Genotype: Ssyy Phenotype: round and green Genotype: Ssyy Phenotype: round and green sY Genotype: ssYy Phenotype: wrinkly and yellow Genotype: ssYy Phenotype: wrinkly and yellow Genotype: ssYy Phenotype: wrinkly and yellow Genotype: ssYy Phenotype: wrinkly and yellow sy Genotype: ssyy Phenotype: wrinkly and green Genotype: ssyy Phenotype: wrinkly and green Genotype: ssyy Phenotype: wrinkly and green Genotype: ssyy Phenotype: wrinkly and green What fraction of the offspring would be predicted to have wrinkly, yellow peas? 4/16, or ¼ or 25% There are many human diseases that are caused by harmful, recessive alleles. Do some research and look one up. Give me the background information on the disease and what populations it is most common in. Are there any hypotheses to explain why the disease is found in the populations? Why is the recessive gene still around? Research this for yourself.