Three Point Linkage Problems 1. Purebred male white mice with short tails and big ears are crossed to purebred black mice with long tails and small ears. All of the progeny are black, with short tails, and big ears. These progeny are crossed with white mice with long tails and small ears. The results of this second cross are given below. Fur color White White White White Black Black Black Black Tail length Short Short Long Long Short Short Long Long Ear size Big Small Big Small Big Small Big Small Number of Progeny 666 14 6 314 314 6 14 666 a. Define the inheritance pattern of each trait Fur color: Dominant = _______________ Recessive = ________________ - Represented by the letter __________ Tail Length: Dominant = _______________ Recessive = ________________ - Represented by the letter __________ Ear size: Dominant = _______________ Recessive = ________________ - Represented by the letter __________ Using the letters you just assigned: What are the parental chromosomes? Which chromosomes represent the double crossovers? Which gene is in the center of the other two? Draw a map of your chromosome below. Then use the data to calculate the distances between each gene. SHOW YOUR WORK. 2. In garden peas, the following cross was made between purebred plants. tall, red flower, round seed X short, white flower, wrinkled seed The progeny were all medium height, pink flowered, wrinkled seed. These progeny peas were crossed to short, white flowered, round seed peas. The results of this cross were: Height Color Seed Number of Progeny Short White Wrinkled 340 Short Pink Wrinkled 340 Medium White Round 340 Medium Pink Round 340 Medium White Wrinkled 160 Medium Pink Wrinkled 160 Short White Round 160 Short Pink Round 160 b. Define the inheritance pattern of each trait Fur color: Dominant = _______________ Recessive = ________________ - Represented by the letter __________ Tail Length: Dominant = _______________ Recessive = ________________ - Represented by the letter __________ Ear size: Dominant = _______________ Recessive = ________________ - Represented by the letter __________ What type of cross was done to get the F2 generation? What are the expected ratios of phenotypes? Are these genes linked? Explain. If so, map out your genes and calculate the distance between them. 3. In warthogs, the following autosomal map has been determined. Tusk 5 m.u. hair______10 m.u. Face The trait variations for the genes are as followed: Tusk: points up or out Hair: long or short Face: ugly or uglier A purebred up tusked, long haired, ugly boar is crossed with a purebred out tusked, short haired, uglier sow. The piglets have upturned tusks, medium hair, are uglier. What are the rules of expression (inheritance patterns) for these genes? (which is dominant, which is recessive) The piglets grow up, and someone is foolish enough to let them breed. 80 offspring are produced. What gametes are made and in what frequency? (in other words, work backwards. You are filling numbers into the data chart that we usually give you!) 4. In the flowering plants called Four O'clocks, there is a single gene controlling flower color, another controlling leaf color, and a third controlling height. The following cross is done. Purebred White flowers, green leaves, short plants X Purebred Red flowers, purple leaves, tall plants F1 Pink flowers, purple leaves, tall plants The F1 plants were crossed to short plants with red flowers, green leaves. The progeny of this cross are: Flower Leaves Height 36% Red purple tall 36% Pink green short 9% Red green 9% pink purple short 4% Red green short 4% pink purple tall 1% red 1% pink purple green tall short tall. A. Define the rules of expression for these alleles of these genes. Make sure you define your symbols clearly. B. Define the linkage relationships for these genes.