Textbook Question
In a diploid plant species, an F₁ with the genotype Gg Ll Tt is test-crossed to a pure-breeding recessive plant with the genotype gg ll tt. The offspring genotypes are as follows:
Explain the meaning of this I value.
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Ch. 5 - Genetic Linkage and Mapping in Eukaryotes
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172
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Table of contents
- Ch. 1 - The Molecular Basis of Heredity, Variation, and Evolution64
- Ch. 2 - Transmission Genetics144
- Ch. 3 - Cell Division and Chromosome Heredity81
- Ch. 4 - Gene Interaction87
- Ch. 5 - Genetic Linkage and Mapping in Eukaryotes103
- Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages73
- Ch. 7 - DNA Structure and Replication71
- Ch. 8 - Molecular Biology of Transcription and RNA Processing79
- Ch. 9 - The Molecular Biology of Translation110
- Ch. 10 - Eukaryotic Chromosome Abnormalities and Molecular Organization100
- Ch. 11 - Gene Mutation, DNA Repair, and Homologous Recombination86
- Ch. 12 - Regulation of Gene Expression in Bacteria and Bacteriophage90
- Ch. 13 - Regulation of Gene Expression in Eukaryotes38
- Ch. 14 - Analysis of Gene Function via Forward Genetics and Reverse Genetics72
- Ch. 15 - Recombinant DNA Technology and Its Applications69
- Ch. 16 - Genomics: Genetics from a Whole-Genome Perspective49
- Ch. 17 - Organelle Inheritance and the Evolution of Organelle Genomes27
- Ch. 18 - Developmental Genetics43
- Ch. 19 - Genetic Analysis of Quantitative Traits66
- Ch. 20 - Population Genetics and Evolution at the Population, Species, and Molecular Levels105
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
Chapter 5, Problem 18b
The Rh blood group in humans is determined by a gene on chromosome 1. A dominant allele produces Rh+ blood type, and a recessive allele generates Rh-. Elliptocytosis is an autosomal dominant disorder that produces abnormally shaped red blood cells that have a short life span resulting in hereditary anemia. A large family with elliptocytosis is tested for genetic linkage of Rh blood group and the disease. The lod score data below are obtained for the family.
What is Zₘₐₓ for this family?
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Examine the graph provided, which plots the lod score (Z) on the y-axis against the recombination fraction (θ) on the x-axis. The lod score indicates the likelihood of genetic linkage between two loci.
Identify the highest point on the lod score curve. This peak represents Zₘₐₓ, the maximum lod score, which is the strongest evidence for linkage.
Determine the corresponding θ value at the peak of the curve. This θ value represents the recombination fraction at which the maximum lod score occurs.
Note that a lod score of 3 or higher is considered significant evidence for linkage. Verify that Zₘₐₓ meets this threshold.
Conclude that Zₘₐₓ is the highest lod score observed on the graph, and the corresponding θ value indicates the estimated recombination fraction between the Rh blood group gene and the elliptocytosis gene.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Lod Score
The Lod (logarithm of the odds) score is a statistical measure used to evaluate the likelihood of genetic linkage between two loci. A positive Lod score indicates that the loci are likely to be linked, while a negative score suggests they are not. A Lod score of 3 or higher is typically considered significant evidence for linkage, meaning the probability of linkage is at least 1000 times greater than that of no linkage.
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Genetic Linkage
Genetic linkage refers to the tendency of genes located close to each other on a chromosome to be inherited together during meiosis. This phenomenon occurs because the closer two genes are, the less likely they are to be separated by recombination. Understanding genetic linkage is crucial for mapping traits and diseases to specific chromosomal locations, as seen in the analysis of the Rh blood group and elliptocytosis.
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Autosomal Dominant Inheritance
Autosomal dominant inheritance is a pattern of genetic transmission where only one copy of a dominant allele is sufficient to express a trait or disorder. In this mode of inheritance, affected individuals have a 50% chance of passing the trait to their offspring. Elliptocytosis, as mentioned in the question, is an example of an autosomal dominant disorder, which influences the analysis of genetic linkage with the Rh blood group.
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Related Practice
Textbook Question
The table given here lists the arrangement of alleles of linked genes in dihybrid organisms, the recombination frequency between the genes, and specific gamete genotypes. Using the information provided, determine the expected frequency of the listed gametes. Assume one map unit equals 1% recombination and, when three genes are involved, interference is zero.
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Textbook Question
The Rh blood group in humans is determined by a gene on chromosome 1. A dominant allele produces Rh+ blood type, and a recessive allele generates Rh-. Elliptocytosis is an autosomal dominant disorder that produces abnormally shaped red blood cells that have a short life span resulting in hereditary anemia. A large family with elliptocytosis is tested for genetic linkage of Rh blood group and the disease. The lod score data below are obtained for the family.
From these data, can you conclude that Rh and elliptocytosis loci are genetically linked in this family? Why or why not?
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Textbook Question
The Rh blood group in humans is determined by a gene on chromosome 1. A dominant allele produces Rh+ blood type, and a recessive allele generates Rh-. Elliptocytosis is an autosomal dominant disorder that produces abnormally shaped red blood cells that have a short life span resulting in hereditary anemia. A large family with elliptocytosis is tested for genetic linkage of Rh blood group and the disease. The lod score data below are obtained for the family.
Over what range of θ do lod scores indicate significant evidence in favor of genetic linkage?
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Textbook Question
Genetic linkage mapping for a large number of families identifies 4% recombination between the genes for Rh blood type and elliptocytosis (see Problem 18). At the Rh locus, alleles R and r control Rh+ and Rh- blood types. Allele E producing elliptocytosis is dominant to the wild-type recessive allele e. Tom and Terri each have elliptocytosis, and each is . Tom's mother has elliptocytosis and is Rh- while his father is healthy and has Rh+. Terri's father is Rh+ and has elliptocytosis; Terri's mother is Rh- and is healthy.
What is the probability that the first child of Tom and Terri will be Rh− and have elliptocytosis?
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Textbook Question
Genetic linkage mapping for a large number of families identifies 4% recombination between the genes for Rh blood type and elliptocytosis (see Problem 18). At the Rh locus, alleles R and r control Rh+ and Rh- blood types. Allele E producing elliptocytosis is dominant to the wild-type recessive allele e. Tom and Terri each have elliptocytosis, and each is . Tom's mother has elliptocytosis and is Rh- while his father is healthy and has Rh+. Terri's father is Rh+ and has elliptocytosis; Terri's mother is Rh- and is healthy.
What is the probability that a child of Tom and Terri who is Rh+ will have elliptocytosis?
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