Concept explainers
a.
To determine: The recombination ferqeuncy between alleles a and b and also between b and c.
Introduction. Recombination is the process that is exclusive to the meiotic division as it allows the exchange of genetic material between the non-homologous chromosomes. The recombination process is responsible for the shuffling of the characters and producing a zygote that is different from both the parents but have the chromosomes from both the parents.
b.
To determine: The coefficient of coincidence.
Introduction. The process of
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Introduction to Genetic Analysis
- Familial retinoblastoma, a rare autosomal dominant defect, arose in a large family that had no prior history of the disease. Consider the following pedigree (the darkly colored symbols represent affected individuals): a. Circle the individual(s) in which the mutation most likely occurred. b. Is the person who is the source of the mutation affected by retinoblastoma? Justify your answer. c. Assuming that the mutant allele is fully penetrant, what is the chance that an affected individual will have an affected child?arrow_forwardAnother cross in Drosophila involved the recessive, X-linked genes yellow (y), white (w) and cut (ct). A yellow-bodied, white-eyed female with normal wings was crossed to a male whose eyes and body were normal but whose wings were cut. The F1 females were wild type for all three traits, while the F1 males expressed the yellow-body and white eyes traits. The cross was carried to an F2 progeny and only male offspring were tallied. Based on the data shown here, a genetic map was constructed. a) Diagram the genotypes of the F1 parents. b) Construct a map, assuming the white is at locus 1.5 on the X-chromosome. Phenotype Male offspring y + ct 9 + w + 6 y w ct 90 + + + 95 + + ct 424 y w + 376 y + + 0 + w ct 0arrow_forwardAnother cross in Drosophila involved the recessive, X-linked genes yellow (y), white (w) and cut (ct). A yellow-bodied, white-eyed female with normal wings was crossed to a male whose eyes and body were normal but whose wings were cut. The F1 females were wild type for all three traits, while the F1 males expressed the yellow-body and white eyes traits. The cross was carried to an F2 progeny and only male offspring were tallied. Based on the data shown here, a genetic map was constructed. a) Diagram the genotypes of the F1 parents. b) Construct a map, assuming the white is at locus 1.5 on the X-chromosome *******ANSWER PART B NOT PART A!!!! Phenotype Male offspring y + ct 9 + w + 6 y w ct 90 + + + 95 + + ct 424 y w + 376 y + + 0 + w ct 0arrow_forward
- In Drosophila, the gene for wing type is known to be autosomal with vestigial wings (vg) known to the recessive to normal, long wings (+). You are already familiar with the white eye gene (w) from lecture with the normal color being red (+). Answer the following questions assuming an initial cross (P1) between a pure breeding white eyed, long winged female and a pure breeding red eyed vestigial winged male. a) What are the parental genotypes? b) What phenotypes would occur in the F1 generation and in what proportions? c) What would the phenotypes and phenotypic ratios would occur in F2 generation?arrow_forwardAnother cross in Drosophila involved the recessive, X-linked genes yellow (y), white (w), and cut (ct). A yellow-bodied, white-eyed female with normal wings was crossed to a male whose eyes and body were normal but whose wings were cut. The F1 females were wild type for all three traits, while the F1 males expressed the yellow-body and white-eye traits. The cross was carried to an F2 progeny, and only male offspring were tallied. On the basis of the data shown here, a genetic map was constructed. Phenotype Male Offspring y + ct 9 + w + 6 y w ct 90 + + + 95 + + ct 424 y w + 376 y + + 0 + w ct 0 (a) Diagram the genotypes of the F1 parents. (b) Construct a map, assuming that white is at locus 1.5 on the X chromosome. (c) Were any double-crossover offspring expected? (d) Could the F2 female offspring be used to construct the map? Why or why not?arrow_forwardIn humans, hemophilia is an X-linked recessive disorder that affects the gene for factor VIII protein, which is essential for blood clotting. The dominant and recessive alleles for the factor VIII gene are represented by H and h. Albinism is an autosomal recessive condition involving the tyrosinase enzyme which synthesizes pigment. Alleles of tyrosinase are represented by A and a. The provided pedigree shows a new marriage between Clara and Charles. A) Review the pedigree, filling in any genotypes that can be determined from the displayed traits. B) What is the probability that their first child will display hemophilia, albinism, or BOTH hemophilia AND albinism.C) If Clara and Charles first child has albinism, what is the probability that the second child will also display albinism?arrow_forward
- Anhidrotic ectodermal dysplasia is an X-linked recessive disorder in humans characterized by small teeth, no sweat glands, and sparse body hair. This trait is usually seen in men, but women who are heterozygous carriers of the trait often have irregular patches of skin with few or no sweat glands (see the illustration below). a. Explain why women who are heterozygous carriers of a recessive gene for anhidrotic ectodermal dysplasia have irregular patches of skin lacking sweat glands. b. Why does the distribution of the patches of skin lacking sweat glands differ among the females depicted in the illustration, even between the identical twins?arrow_forwardVermillion eye color in Drosophila is a sex-linked recessive trait. What phenotype would be found in this progeny of a cross between a vermillion female and a wild type male?arrow_forwardA standard three-point mapping is conducted for recessive mutations in autosomal genes purple eye (pr), curved wing ( c) and black body (b). Their wild type alleles are also used for genetic mapping. An F1 Drosophila female heterozygous for purple eye (pr), curved wing (c) and black (b) is crossed to a triply homozygous mutant male. The observed numbers and phenotypes of the offspring are as follows: 360 pr c b 380 pr+ c+ b+ 104 pr c+ b 96 pr+ c b+ 30 pr c b+ 20 pr+ c+ b 6 pr c+ b+ 4 pr+ c b PROVIDE THE FOLLOWING: A) State the order of genes on this chromosome. B) Calculate map distances between the gene pairs: pr-c, pr-b, c-b. Show calculations, state the number of map units and which gene pairs they refer to.arrow_forward
- Two fruit flies (Drosophila melanogaster) were crossed. The cross was between a homozygous red-eyed, wingless female and a white-eyed male heterozygous for wings. Recall that red eyes (R) is dominant over white eyes (r) and is inherited on the X chromosome (sex-linked) and as such, eye colour alleles should be written as superscript. In addition, the autosomal trait wings (W) is dominant over wingless (w). 1. List the female genotype 2. List the male genotype 3. Construct a Punnett Square for this dihybrid cross on a piece of paper, to determine what the offspring of such a cross would be with respect to sex, eye colour & wings. 4. Using the information from your Punnett Square answer the following: a. What genotypes did you get (list all genotype combinations; if you have more than one of the same kind, you do NOT have to re-list it.) b. What are the phenotypic ratios of the offspring with respect to sex, eye colour and wings?arrow_forwardIN DROSOPHILA, AN X-LINKED RECESSIVE MUTATION, Xm CAUSES MINIATURE WINGS. LIST THE F₂ PHENOTYPIC RATIOS IF: A MINIATURE-WINGED FEMALE IS CROSSED WITH A NORMAL MALE AND A MINIATURE-WINGED MALE IS ● ● CROSSED WITH A NORMAL FEMALE. WHAT WOULD THE PHENOTYPIC RATIO FROM (A) BE IF THE MINIATURE- WINGED GENE WERE AUTOSOMAL? ASSUME IN ALL CASES THAT THE P1 INDIVIDUALS ARE TRUE-BREEDING.arrow_forwardIn Drosophila, an X-linked recessive mutation, (s) causes irregular wing margins. Give the genotypes, phenotypes and phenotypic ratio of the F1 and F2 offspring in the following crosses a. scalloped female crossed with a normal male b. scalloped male crossed with a homozygous normal female. Compare these results to those that would be obtained if the scalloped gene is autosomal.arrow_forward
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