Concept explainers
A recessive allele in mice results in an unusally long neck. Sometimes, during early embryonic development, the long neck causes the embryo to die. An experimenter began with a population of true-breeding normal mice and true-breeding mice with long necks. Crosses were made between these two populations to produce an
522 mice with normal necks
62 mice with long necks
What percentage of homozygous mice (that would have had long necks if they had survived) died during embryonic development?
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Genetics: Analysis and Principles
- A pet shop owner who specialized in breeding smooth coated white guinea pigs decided to introduce a new line of guinea pigs. He felt that a rough coated white animal would be very popular, and to develop such an animal he ordered a pair of guinea pigs from another breeder who specialized in rough coated tan animals. The pet shop owner then crossed the new rough tan male with one of his smooth white females. All of the offspring from this cross had tan fur and rough coats. The shop owner was disappointed but set out to solve his problem by trying the five approaches below. Which one of the five would have the best chance of producing a rough coated white animal Crossed two smooth white guinea pigs. Crossed a rough tan male offspring from his first cross with a rough tan female offspring from his first cross. Crossed the pair of rough tan animals he had obtained from the other breeder. Crossed a rough tan male offspring from his first cross with a smooth white female.…arrow_forwardAs a hypothetical example, a trait in mice results in abnormallylong tails. You initially have a true-breeding strain with normaltails and a true-breeding strain with long tails. You then make thefollowing types of crosses:Cross 1: When true-breeding females with normal tails arecrossed to true-breeding males with long tails, all F1 offspringhave long tails.Cross 2: When true-breeding females with long tails arecrossed to true-breeding males with normal tails, all F1 offspring have normal tails.Cross 3: When F1 females from cross 1 are crossed to true-breeding males with normal tails, all offspring have normal tailsCross 4: When F1 males from cross 1 are crossed to truebreeding females with long tails, half of the offspring havenormal tails and half have long tails.Explain the pattern of inheritance of this trait.arrow_forwardOn a fox ranch in Scandinavia, a mutation arose that yielded a “platinum” coat color. The platinum color proved very popular in the fox coat trade, but, in spite of enormous effort on the part of fox breeders, a pure- breeding platinum strain was never achieved. Every time that two platinum fox were crossed, some wild-type offspring appeared in the progeny. For example, the repeated crosses of a single pair of platinum fox produced 83 platinum and 38 wild-type progeny. All other such crosses gave similar progeny ratios. State the genetic hypothesis that accounts for these results.arrow_forward
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- Two recessive traits in mice are droopy ears and flaky tails. A true-breeding mouse with normal ears (De) and a flakey tail (ft) was crossed to a true-breeding mouse with droopy ears (de) and a normal tail (Ft). The F1 offspring were then crossed to mice with droopy ears and flaky tails. This cross produced the following 100 offspring... 4 droopy ears, flaky tail 2 normal ears, normal tail 46 normal ears, flaky tail 48 droopy ears, normal tail 1) Looking at the offspring, do you believe the genes are linked or unlinked? Support your answer. 2) What is the genotype of the P1 generation organisms? 3) What is the genotype of the F1 generation? DELLarrow_forwardA population geneticist collected 400 deer mice from the wild. All have normal ears. She raised about 800 animals in each of the following four generations (random mating) and found that all except one male in the fourth generation had normal ears. This male was earless but was otherwise wild-type and fertile. Suggest 3 possible causes that could lead to the appearance of this earless male. What kinds of experimental crosses would you carry out to distinguish between these three alternatives?arrow_forwardThe parental genotypes for a series of crosses are wild-type male fruit flies mated to females with white eyes (wh) and miniature (min) wings. The phenotypes of the F1 generation were wild-type females, and males with white eyes, and miniature wings. These flies were allowed to mate with each other and produced the following offspring: Red eyes, long wings White eyes, miniature wings Red eyes, miniature wings White eyes, long wings 770 716 401 318 Total 2205 A. Are these genes linked? Why or why not?arrow_forward
- In guinea pigs, rough coat (R) is dominant to smooth coat (r). If a homozygous rough-coated animal is crossed with a smooth-coated one: What will be the phenotype(s) of the F1 generation? What will be the phenotype(s) of the F2 generation? What will be the phenotype(s) of the offspring resulting from a cross of an F1 individual back to its rough parent? What will be the phenotype(s) of the offspring of a cross of an F1 individual back to its smooth parent?arrow_forwardA geneticist has two true-breeding strains of mice. Each strain is homozygous for an independently discovered dominant mutation that causes the mice to have no fur. One mutant strain is called “hairless”, and the other strain is called “naked”. The geneticist crosses hairless and naked mice with each other and the F1 offspring all have no fur. When the F1 mice are crossed with each other, the offspring consist of 187 mutant mice with without fur and 13 normal mice with fur. a. Are the “hairless” and “naked” mutations alleles of the same gene? Give a reason for your answer. b. Give the genotypic and associated phenotypic ratios of the F2 offspring. (which genotypes in the offspring of the F1 x F1 cross produce fur and which genotypes produce no fur). In another strain of mice, coat colour is controlled by a single gene with multiple alleles in a dominance series where cream (A1) > agouti (A2) > brown (A3) > black (A4). c. Give the genotypes of two phenotypically…arrow_forwardWhen crossing a true breeding white mouse with a true breeding brown mouse your friend tells you she recovered all black mice. But then when she crosses the F1 mice to each other she recovered 28 black mice, 8 brown mice, and 13 white mice. Can you help her explain these results? (Type out the cross and include genotypes of as many mice as possible. What phrase best describes this phenomenon? How many genes are involved are they linked or unlinked? Etc.)arrow_forward
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