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Ch. 5 - Genetic Linkage and Mapping in Eukaryotes
Sanders - Genetic Analysis: An Integrated Approach 3rd Edition
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
All textbooksSanders 3rd EditionCh. 5 - Genetic Linkage and Mapping in EukaryotesProblem 29b
Chapter 5, Problem 29b

A 2006 genetic study of a large American family (Ikeda et al., 2006) identified genetic linkage between DNA markers on chromosome 11 and the gene producing the autosomal dominant neuromuscular disorder spinocerebellar ataxia type 5 (SCA5). The following lod score data are taken from the 2006 study:                  
Table displaying lod score data for genetic linkage between SCA5 and DNA markers A and B across various theta values.
What is the maximum value for each set of lod scores?

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Understand the problem: The goal is to determine the maximum lod score for each set of lod scores provided in the table. Lod scores are used in genetic linkage analysis to evaluate the likelihood of a genetic marker being linked to a trait of interest at various recombination fractions (θ).
Identify the two sets of lod scores: The first set corresponds to SCA5 and DNA marker A, and the second set corresponds to SCA5 and DNA marker B. Each set has lod scores listed for different θ values (0.01, 0.05, 0.10, 0.20, 0.30, 0.40).
For the first set (SCA5 and DNA marker A), compare the lod scores: 11.02, 12.26, 11.94, 10.04, 7.26, and 3.77. Identify the maximum value among these scores.
For the second set (SCA5 and DNA marker B), compare the lod scores: 0.35, 0.94, 1.07, 0.99, 0.75, and 0.43. Identify the maximum value among these scores.
Conclude by stating the maximum lod score for each set and the corresponding θ value where the maximum occurs. This provides insight into the most likely recombination fraction for linkage between the gene and the DNA markers.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Lod Score

A lod score (logarithm of the odds) is a statistical measure used in genetics to evaluate the likelihood of genetic linkage between a trait and a specific genetic marker. A higher lod score indicates a greater probability that the two loci are linked, with a score of 3 or higher typically suggesting significant linkage. This concept is crucial for interpreting the data presented in genetic studies.
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Theta (θ) Value

Theta (θ) represents the recombination fraction, which is the probability that a crossover will occur between two loci during meiosis. It ranges from 0 to 0.5, where 0 indicates complete linkage and 0.5 indicates independent assortment. Understanding theta values is essential for analyzing lod scores, as they directly influence the calculation of genetic linkage.
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Step 3

Autosomal Dominant Inheritance

Autosomal dominant inheritance is a pattern of genetic transmission where only one copy of a mutated gene from an affected parent can cause the disorder in offspring. This means that the trait can be expressed even if only one allele is mutated. Recognizing this inheritance pattern is vital for understanding the implications of the genetic study on spinocerebellar ataxia type 5 (SCA5) and its familial transmission.
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Related Practice
Textbook Question

Neurofibromatosis 1 (NF1) is an autosomal dominant disorder inherited on human chromosome 17. Part of the analysis mapping the NF1 gene to chromosome 17 came from genetic linkage studies testing segregation of NF1 and DNA genetic markers on various chromosomes. A DNA marker with two alleles, designated 1 and 2, is linked to NF1. The pedigree below shows segregation of NF1 (darkened symbols) and gives genotypes for the DNA marker for each family member.

Based on the phase of alleles on chromosomes in generation II, is there any evidence of recombination among the eight offspring in generation III? Explain.

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Textbook Question

Neurofibromatosis 1 (NF1) is an autosomal dominant disorder inherited on human chromosome 17. Part of the analysis mapping the NF1 gene to chromosome 17 came from genetic linkage studies testing segregation of NF1 and DNA genetic markers on various chromosomes. A DNA marker with two alleles, designated 1 and 2, is linked to NF1. The pedigree below shows segregation of NF1 (darkened symbols) and gives genotypes for the DNA marker for each family member.

What is the estimated recombination frequency between the NF1 gene and the DNA marker?

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Textbook Question

A 2006 genetic study of a large American family (Ikeda et al., 2006) identified genetic linkage between DNA markers on chromosome 11 and the gene producing the autosomal dominant neuromuscular disorder spinocerebellar ataxia type 5 (SCA5). The following lod score data are taken from the 2006 study:                  

Does either group of lod scores indicate statistically significant odds in favor of genetic linkage? Explain your answer.

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Textbook Question

A 2006 genetic study of a large American family (Ikeda et al., 2006) identified genetic linkage between DNA markers on chromosome 11 and the gene producing the autosomal dominant neuromuscular disorder spinocerebellar ataxia type 5 (SCA5). The following lod score data are taken from the 2006 study:                  

Based on the available information, is DNA marker A linked to the gene producing SCA5? Explain your answer.

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Textbook Question

A 2006 genetic study of a large American family (Ikeda et al., 2006) identified genetic linkage between DNA markers on chromosome 11 and the gene producing the autosomal dominant neuromuscular disorder spinocerebellar ataxia type 5 (SCA5). The following lod score data are taken from the 2006 study:

Based on available information, is DNA marker B linked to the gene for SCA5? Explain your answer.

592
views
Textbook Question

A Drosophila experiment examining potential genetic linkage of X-linked genes studies a recessive eye mutant (echinus), a recessive wing-vein mutation (crossveinless), and a recessive bristle mutation (scute). The wild-type phenotypes are dominant. Trihybrid wild-type females (all have the same genotype) are crossed to hemizygous males displaying the three recessive phenotypes. Among the 20,765 progeny produced from these crosses are the phenotypes and numbers listed in the table. Any phenotype not given is wild type.

Determine the gene order and identify the alleles on the homologous X chromosomes in the trihybrid females.

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