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Assume that genes, A and B are on the same chromosome and are 50 map units apart. An animal heterozygous at both loci is crosscd with one that is homozygous recessive at both loci. What percentage of the offspring will show recombinant
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- Please explain your choice: Consider an individual with genotype A/a B/b C/c D/d, descended from one parent with genotype A/A B/B C/C D/D and another parent with genotype a/a b/b c/c d/d. Assume that genes A, B, C, and D are present in this particular order on the same chromosome. What is the minimum number of crossovers that must take place on that chromosome for the individual to generate a gamete with genotype AbCd? (hint: draw homologous chromatids and the crossovers that are taking place between them)arrow_forwardA female of genotype a b c + + + produces 100 meiotic tetrads. Of these, 68 show no crossover events. Of the remaining 32, 20 show a crossover between a and b, 10 show a crossover between b and c, and 2 show a double crossover between a and b and between b and c. Of the 400 gametes produced, how many of each of the 8 different genotypes will be produced? Assuming the order a–b–c and the allele arrangement previously shown, what is the map distance between these loci?arrow_forwardConsider a cross between a true breeding purple flowered pea plant (genotype PP) and a true breeding white flowered pea plant (genotype pp) that produces all heterozygous F1 offspring. An F1 intercross is conducted between two of the F1 offspring, resulting in the F2 generation. What is the expected phenotype outcome of the F2 individuals resulting from the F1 intercross? 100% white offspring 100% purple offspring 3 purple: 1 white 1 purple: 2 light purple: 1 white 1 purple: 1 whitearrow_forward
- In corn (Zea mays), the wild type trait is for kernels to be round; some kernels are shrunken (S), which is caused by recessive, mutant alleles of various genes. You obtain five strains of corn with shrunken kernels, and conduct pairwise crosses between all five strains (1x1, 1x2, 1,3, etc). The results are summarized in the matrix below: if the offspring have the wild type trait, round, then they are represented with a "+"; if the offspring have the trait caused by recessive, mutant alleles, shrunken, they are marked with "S" 1 2 3 4 5 1 S 2 + S 3 + 4 5 + S S S S S S + + + S a. How many total genes are represented by these five strains? Explain your answer. b. Which of the five strains represent the same genes? (how can they be grouped, if at all). Explain your answer.arrow_forwardIn the mapping example in Fig 2, the dominant alleles were on one chromosome and the recessive alleles were on the homolog. Let’s consider a twofactor cross in which the dominant allele for one gene is on onechromosome, but the dominant allele for a second gene is on thehomolog. A cross is made between AAbb and aaBB parents. The F1offspring are AaBb. The F1 heterozygotes are then testcrossed to aabbindividuals. Which F2 offspring are recombinant?arrow_forwardIn the mapping example in Fig 2, the dominant alleles were on one chromosome and the recessive alleles were on the homolog. Let’s consider a twofactor cross in which the dominant allele for one gene is on onechromosome, but the dominant allele for a second gene is on thehomolog. A cross is made between AAbb and aaBB parents. The F1offspring are AaBb. The F1 heterozygotes are then testcrossed to aabbindividuals. What topic in genetics does this question address?arrow_forward
- Two genes, A and B, are 10 map units apart along the same chromosome. A cross was made between AAbb and aaBB individuals to produce AaBb F1 offspring. The F1 offspring were then crossed to aabb individuals to yield an F2 generation. What would be the genotype(s) of F2 offspring that carry recombinant chromosomes? (Note: recombinant chromosomes are the product of crossing over). What percentage of F2 offspring would be Aabb?arrow_forwardIn onion, male sterility is produced when the nuclear genotype is aa and the mitochondrial gene S (sterile) are present. Any other combination of nuclear genotype and mitochondrial gene (including gene F for fertile) will result in a male fertile plant. Give the genotypic ratio and the phenotypic ratio or the percentage of male sterile and male fertile offspring that will be produced in the following crosses. 1. Aa + S male x aa + F female 2. Reciprocal cross of number 1. (Note that when we do reciprocal cross, we interchange/swap the genotypes of the parents (if there is a nuclear gene involved, you interchange the nuclear genotype as well). 3. Aa + S female x Aa + F male 4. Reciprocal cross of number 3.arrow_forwardIn silkmoths (Bombyx mori), red eyes (re) and white-banded wings (wb) are encoded by two mutant alleles that are recessive to those that produce wild-type traits (re+ and wb+); these two genes are on the same chromosome. A moth homozygous for red eyes and white-banded wings is crossed with a moth homozygous for the wild-type traits. The F1 have wild-type eyes and wild-type wings. The F1 are crossed with moths that have red eyes and white-banded wings in a testcross. The progeny of this testcross are wild-type eyes, wild-type wings red eyes, wild-type wings wild-type eyes, white-banded wings red eyes, white-banded wings a. What phenotypic proportions would be expected if the genes for red eyes and for white-banded wings were located on different chromosomes? b. What is the rate of recombination between the gene for red eyes and the gene for white-banded wings?arrow_forward
- In the snail Limnaea peregra, coiling of the shell is determined by the genes D for right-hand coiled shells, and d for left-hand coiled shells. The gene for the right-hand coiled shell is dominant. The direction of coiling is determined by the genotype of the maternal parent producing the egg, regardless of the progeny's genotype. Which of the following crosses could give a left-hand coiled shell heterozygote? A. right-hand coiled dd female X left-hand coiled DD male B. left-hand coiled DD female X right-hand coiled dd male C. left-hand coiled DD female X left-hand coiled DD male D. right-hand coiled dd female X left-hand coiled dd malearrow_forwardConsider five unlinked genes: a, b, c, d, e are the recessive alleles, and A, B, C, D, E are the dominant alleles. Now if two quintuple heterozygote individuals are crossed, what is the probability of getting an offspring with the dominant phenotype for the loci A, B, and C, but any genotype for the D and E loci? 3/4 = 0.75 1/4 = 0.25 9/64 = 0.141 1/64 = 0.0156 27/64 = 0.422arrow_forwardAssume that the trihybrid cross AABBrr x aabbRR is made in a plant species. Assume that A and B are dominant alleles, but there is no dominance effect of alleles at the R locus. a) How many different gametes are possible in the F1generation? What are the genotypes of these gametes? b) What is the probability of the parental aabbRR genotype in the F2 progeny? c) What proportion of the F2 progeny would be expected to be homozygous for all three genes?arrow_forward
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