Concept explainers
In laboratory class, a genetics student was assigned to study an unknown mutation in Drosophila that had a whitish eye. He crossed females from his true-breeding mutant stock to wild-type (brick-red-eyed) males, recovering all wild-type F1 flies. In the F2 generation, the following offspring were recovered in the following proportions:
The student was stumped until the instructor suggested that perhaps the whitish eye in the original stock was the result of homozygosity for a mutation causing brown eyes and a mutation causing bright red eyes, illustrating gene interaction (see Chapter 4). After much thought, the student was able to analyze the data, explain the results, and learn several things about the location of the two genes relative to one another. One key to his understanding was that crossing over occurs in Drosophila females but not in males. Based on his analysis, what did the student learn about the two genes?
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Concepts of Genetics (11th Edition)
- To determine the recombination frequency between body color and wing genes in flies, you perform several crosses where you cross an F1 having red body and smooth wings with a yellow-bodied, crinkle-winged fly. You get the following results. What is the distance between the genes for body color and wing surface in map units?arrow_forwardIn Drosophila, males from a true-breeding stock with raspberry-colored eyes were mated to females from a true-breeding stock with sable-colored bodies. In the F1 generation, all the females had wild-type eye and body color, while all the males had wild-type eye color but sable-colored bodies. When F1 males and females were mated to each other, the F2 was composed of: 216 females with wild-type eyes and wild-type bodies 223 females with wild-type eyes and sable bodies 191 males with wild-type eyes and sable bodies 188 males with raspberry eyes and wild-type bodies 23 males with wild-type eyes and bodies 27 males with raspberry eyes and sable bodies Which statements are consistent with the above data? (Select all correct answers.) The alleles causing the raspberry-colored eye and sable-colored body phenotypes are dominant to the corresponding wild-type alleles The genes controlling raspberry-colored eyes and sable-colored bodies map…arrow_forwardTwo pure-breeding strains of flies are mated, and the F1 are intercrossed. The first strain has curled wings and black bodies. The second strain has straight wings and brown bodies. The F2 progeny are 271 straight wings with brown bodies, 31 curled wings with black bodies, 94 curled wings with brown bodies and 90 straight wings with black bodies. If the F1 were backcrossed to the straight, wing brown bodied parent, what phenotypes would be produced among the progeny? What would be the proportion of each phenotype?arrow_forward
- Females of wild-type Strain A and males of mutant Strain B, as well as females of mutant Strain B and males of wild-type Strain A, make reciprocal crosses. Explain why reciprocal crosses are needed in genetics experiments involving Drosophila fruit flies.arrow_forwardIn Drosophila, males from a true-breeding stock with raspberry-colored eyes (instead of normal brownish-red eyes) were mated to females from a true-breeding stock with sable- colored bodies (instead of normal brown bodies). In the F, generation, all the females had wild-type eye and body color, while all the males had wild-type eye color but sable-colored bodies. When F, males and females were mated, the F generation was composed of: 216 females with wild-type eyes and bodies 223 females with wild-type eyes and sable bodies 191 males with wild-type eyes and sable bodies 188 males with raspberry eyes and wild-type bodies 23 males with wild-type eyes and bodies 27 males with raspberry eyes and sable bodies. Explain these results by diagramming the crosses and calculating any relevant map distances.arrow_forwardTwo different strains of Drosophila, strain A and strain B, each has a recessive mutation that results in abnormally bright red eye color. (Wild type flies have brownish red eye color). When a homozygous strain A fly is crossed with a homozygous B fly, all of the progeny have the dominant wild type eye color. The wild type-eyed progeny were allowed to breed among themselves to produce the F2 generation. The F2 generation consisted of 92 wild type and 74 bright red-eyed flies. Write the genotype(s) of the flies in each generation. Use a low dash (e.g. A_ B_) to indicate genotypes that could be either homozygous or heterozygous) a) parental strain A b) parental strain B c) wild type progeny (F1) d) wild type F2 e) bright-eyed F2arrow_forward
- In a particular organism, the A locus and the D locus are so tightly linked that no crossing over is ever observed between them. If an AADD individual is crossed to an aadd individual, what types of gametes will their double-heterozygote F1 offspring produce and in what proportions? Group of answer choices 25% parental and 75% recombinant gametes 75% parental and 25% recombinant gametes 100% parental and 0% recombinant gametes 50% parental and 50% recombinant gametes 0% parental and 100% recombinant gametesarrow_forwardIn flies, assume black (B) is dominant and green (b) is recessive for abdomen color, and straight (S) is dominant and bent (s) is recessive for antenna shape. Assume also that these genes are found on the same chromosome. If single mutants for each of these genes (green abdomen x bent antenna) are crossed with one another, and you then testcross the resulting offspring, you get the following numbers of each phenotype: black, straight 17 green, bent 12 black, bent 337 green, straight 364 What is the map distance between B and S? You must show and clearly label ALL workarrow_forwardCross Cross A Cross A Cross B Cross B Phenotype F1 generation F2 generation F1 generation F2 generation Male red eyes 132 150 0 99 Female red eyes 135 295 110 101 Male white eyes 0 147 105 93 Female white eyes 0 0 0 95 Using “+” to indicate the wildtype red-eyed allele and “w” to indicate the mutant white-eyed allele, state the genotypes of the following: Wildtype red-eyed and white-eyed parental flies from cross A and cross B. Males and females from the F1 generation flies from cross A and cross B Males and females, F2 generation flies from cross A and cross B.arrow_forward
- In a diploid plant species, an F1 with the genotype Mm Rr Ss is test crossed to a pure breeding recessive plant with the genotype mm rr ss. The offspring genotypes are as follows: Genotype Number Mm Rr Ss 687 Mm Rr ss 5 Mm rr Ss 68 Mm rr ss 196 mm Rr Ss 185 mm Rr ss 72 mm rr Ss 8 mm rr ss 679 Total 1900 1. What is the gene order of these linked genes?arrow_forwardIn barley, a self-fertilizing species that can be cross-fertilized, two true-breeding strains with virescent leaves occur. In strain A, the trait is caused by a cytoplasmic gene while in strain B it is by a recessive chromosomal gene. What phenotypes would you expect among the progeny, and in what proportions in each of the following? Illustrate your crosses below, indicate and the female and male parent for each cross, and write the phenotype of all the parents and offspring(s). a. reciprocal crosses between A and Bb. crossing of each F1 in (a) to each of the paternal strainsc. self-fertilization of the F1’s in (a)d. reciprocal crosses between F1’s in (a) Use the following gene assignments: Strain A (trait is in Cytoplasm) A – virescent a – not virescent Strain B (recessive chromosomal gene) B – not virescent b - virescentarrow_forwardIn Figure 5-15, how are each of the following genotypesproduced?a. F+ a− c. F− a+b. F− a− d. F+ a+arrow_forward
- Biology (MindTap Course List)BiologyISBN:9781337392938Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. BergPublisher:Cengage Learning