Concept explainers
Gene
a. If
b. If two crossover events occurred between these two genes, what are the genotypes of recombinant chromosomes?
c. Can you make a general statement about how the occurrence of two crossover events between a given pair of linked genes affects the estimate of recombination frequency? (Hint: Think about this problem for a gene pair with a small recombination frequency versus a gene pair with a much higher recombination frequency. See also Figure
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Chapter 5 Solutions
Genetic Analysis: An Integrated Approach (3rd Edition)
- Deduce the phenotypic proportions in the progeny of thefollowing crosses of autotetraploids in which the a+/a locus is very close to the centromere. (Assume that the fourhomologous chromosomes of any one type pair randomly two by two and that only one copy of the a+ allele isnecessary for the wild-type phenotype.)a. a+/a+/a/a × a/a/a /ab. a+/a/a /a × a/a/a/ac. a+/a/a /a × a+/a/a /ad. a+/a+/a /a × a+/a/a /aarrow_forwardAn individual is heterozygous for a reciprocal translocation, with the following chromosomes: A • B C D E F A • B C V W X R S T • U D E F R S T • U V W X a. Draw a picture of these chromosomes pairing in prophase I of meiosis. b. Draw the products of alternate, adjacent-1, and adjacent-2 segregations. c. Explain why the fertility of this individual is likely to be less than the fertility of an individual without a translocation.arrow_forwardWhat is/are the phenotypes of the recombinant offspring of the F2generation?a. red eyes, long wingsb. white eyes, miniature wingsc. red eyes, long wings and white eyes, miniature wingsd. red eyes, miniature wings and white eyes, long wings [Answer the multiple-choice questions based on the following experiment:P generation: True-breeding flies with red eyes and long wings werecrossed to flies with white eyes and miniature wings. All F1 offspringhad red eyes and long wings.The F1 female flies were then crossed to males with white eyes and miniaturewings. The following results were obtained for the F2 generation:129 red eyes, long wings133 white eyes, miniature wings71 red eyes, miniature wings67 white eyes, long wings]arrow_forward
- n corn, male sterility is controlled by maternal cytoplasmic elements. This phenotype renders the male part of the corn plants (i.e the tassel) unable to produce fertile pollen; the female parts, however, remain receptive to pollination by pollen from male fertile corn plants. However, the presence of a nuclear fertility restorer gene F restores fertility to male sterile lines sing the cardboard chips, simulate the crosses indicated below. Give the genotypes and phenotypes of the offsprings in each cross, and properly label the nucleus and the cytoplasm of each individual in the cross Legend male sterile cytoplasm Male fertile cytoplasm FF nucleus Ff nucleus ff nucleus A. Male sterile female x FF male Explain the phenotype of the offspring B. Male sterile female x Ff male Explain the phenotype of the offspringarrow_forwardIn autotetraploid Chinese primrose (Primula sinensis L.), the gene controlling stigma color is very near the centromere of the chromosome carrying it. The allele G for green stigma is dominant to g for red stigmas. A homozygous green autotetraploid strain is crossed with a homozygous red autotetraploid strain. a. What is the genotype of the Fl1? b. Show the types of gametes the Fl's may be expected to form and derive the expected proportion of each. Show your solution. c. What phenotypic ratio of green to red is expected if: the Fl's are intercrossed? Show your solution. the Fl's are crossed with red plants? Show your solution. d. If the G locus were 50 or more map units from the centromere, what types and proportions of gametes would the Fl be expected to produce? Derive the expected F2 phenotypic ratio.arrow_forwardn corn, male sterility is controlled by maternal cytoplasmic elements. This phenotype renders the male part of the corn plants (i.e the tassel) unable to produce fertile pollen; the female parts, however, remain receptive to pollination by pollen from male fertile corn plants. However, the presence of a nuclear fertility restorer gene F restores fertility to male sterile lines Using the cardboard chips, simulate the crosses indicated below. Give the genotypes and phenotypes of the offsprings in each cross, and properly label the nucleus and the cytoplasm each individual in the cross Legend male sterile cytoplasm Male fertile cytoplasm FF nucleus Ff nucleus ff nucleus A. Male sterile female x FF male Explain the phenotype of the offspring B. Male sterile female x Ff male Explain the phenotype of the offspringarrow_forward
- An initial crossover event will occur between A and B, as indicated in the corresponding image. After this initial event occurs, a second cross over event occurs (not illustrated) involving the products of the first crossover event. Given the chromosome organization below, which two chromatids of the bivalent were involved and between which genes did the second crossover event occur to produce the indicated chromosomes? a. A B c, A b c, a B C, and a b C b. A B C, A B C, a b c, and a b c (return to the original crossover depicted in the image, and then determine how the second crossover event produced this arrangementarrow_forwardConsider the following "pericentric" ("around the center") inversion. In one an individual, a simplified 8-gene sequence along one chromosome is 1234 5678 while a pericentric inversion occurred on their other homologous chromosome, resulting in the sequence 1265 4378 (the dot represents the centromere). Draw these homologous chromosomes lined up (as during crossing over, in Prophase l). If a crossover event occurred between gene locus 3 and 4 (slicing between them) on the original chromosome, what would the crossover products look like? What would be the "problem" with each of the chromosomes that result?arrow_forwardIn an autotetraploid Chinese primrose (Primula sinensis), the gene controlling stigma color is very near the centromere of the chromosome carrying it. The allele G for green stigma is dominant to g for red stigmas. A homozygous green autotetraploid strain is crossed with a homozygous red autotetraploid strain. a. What is the genotype of the F1? b. Show the types of gametes the F1’s may be expected to form and derive the expected proportion of each. c. What phenotypic ratio of green to red is expected if: 1. The F1’s are intercrossed? 2. The F1’s are crossed with red plants d. If the G locus were 50 or more map units from the centromere, what types and proportions of gametes would the F1 be expected to produce? Derive the expected F2 phenotypic ratio.arrow_forward
- Two plants in a cross were each heterozygous for two gene pairs (AB /ab) whose loci are linked and 30 map units (mu) apart. (Recall that 1 mu is equal to 1% recombination between two genes.) Assuming that crossing over occurs during the formation of both male and female gametes and that the A and B alleles are dominant, determine the phenotypic ratio of their offspring. Part E: What proportion of the offspring of two plants (both (AB/ab ) will be A - B- if the genes are 30 mu apart? Part F: What proportion of the offspring of two plants (both (AB/ab)) will be A - bb if the genes are 30 mu apart? Part G: What proportion of the offspring of two plants (both (AB/ab)) will be aaB- If the genes are 30 mu apart? Part H: What proportion of the offspring of two plants (both (AB/ab)) will be aabb if the genes are 30 mu apart?arrow_forwardWild-type mice have brown fur and short tails. Loss of function of a particular gene produces white fur, while loss of function of another gene produces long tails, and loss of function at a third locus produces agitated behavior. Each of these loss of function alleles is recessive. If a wild-type mouse is crossed with a triple mutant, and their F1 progeny is test-crossed, the following recombination frequencies are observed among their progeny. Produce a genetic map for these loci. Brown, short tailed, normal: 955 White, short tailed, normal: 16 Brown, short tailed, agitated: 0 White, short tailed, agitated: 36 Brown, long tailed, normal: White, long tailed, normal: Brown, long tailed, agitated: 46 0 14 White, long tailed, agitated: 933arrow_forwardIn an autotetraploid Chinese primrose (Primula sinensis L.), the gene controlling stigma color is very near the centromere of the chromosome carrying it. The allele G for green stigma is dominant to g for red stigmas. A homozygous green autotetraploid strain is crossed with a homozygous red autotetraploid strain. What is the genotype of the F1? Show the types of gametes the F1’s may be expected to form and derive the expected proportion of each. What phenotypic ratio of green to red is expected if: The F1’s are intercrossed? The F1’s are crossed with red plants If the G locus were 50 or more map units from the centromere, what types and proportions of gametes would the F1 be expected to produce? Derive the expected F2 phenotypic ratio.arrow_forward
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