Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

4. Genetic Mapping and Linkage

Mapping Genes

Genetics

4. Genetic Mapping and Linkage

Mapping Genes

Previous problemNext problem

3: minutes

Problem 31a

Textbook Question

A genetic study of an early onset form of heart disease identifies 10 families containing members with the condition. No clear dominant or recessive pattern of inheritance is evident, but an analysis of SNP markers for five families detects a strong association with a marker on chromosome 12, and genetic linkage analysis for the marker produces a lod score of 2.2.

What do the association and lod score results suggest about this genetic marker?

Verified step by step guidance

Understand the problem: The question involves interpreting the results of a genetic study, specifically the association of a SNP marker with a condition and the significance of a LOD score. The goal is to determine what these results suggest about the genetic marker on chromosome 12.

Step 1: Recall the concept of association. A strong association between a SNP marker and a condition suggests that the marker is located near a gene or genetic region that may influence the condition. This is because markers that are physically close to causal genes tend to be inherited together due to linkage disequilibrium.

Step 2: Understand the LOD score. The LOD (logarithm of the odds) score is a statistical measure used in genetic linkage analysis to evaluate the likelihood that a particular marker is linked to a trait. A LOD score of 3 or higher is generally considered strong evidence of linkage, while a score below 2 is considered weak evidence. A score of 2.2 falls in a gray area, suggesting moderate evidence of linkage.

Step 3: Interpret the results. The strong association with the SNP marker on chromosome 12 suggests that this region may contain a gene or genetic element contributing to the early onset heart disease. However, the LOD score of 2.2 indicates that the evidence for linkage is not definitive and further studies are needed to confirm the relationship.

Step 4: Suggest next steps. To strengthen the evidence, researchers could increase the sample size by studying more families, perform fine-mapping to narrow down the region of interest, or use functional studies to identify candidate genes in the region and test their role in the condition.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

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

SNP Markers

Single Nucleotide Polymorphisms (SNPs) are variations at a single position in a DNA sequence among individuals. They are the most common type of genetic variation and can be used as markers in genetic studies to identify associations with diseases. In this context, the strong association of a SNP marker on chromosome 12 with early onset heart disease suggests that this marker may be linked to the genetic factors contributing to the condition.

Lod Score

The lod score (logarithm of the odds) is a statistical measure used to evaluate the likelihood that two loci are linked, compared to the likelihood that they are not linked. A lod score of 2.2 indicates a significant likelihood of linkage, suggesting that the genetic marker on chromosome 12 is likely associated with the heart disease in the studied families. Generally, a lod score above 3 is considered strong evidence for linkage.

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 is important in understanding the inheritance patterns of traits and diseases. In this case, the genetic linkage analysis showing a lod score of 2.2 implies that the marker on chromosome 12 may be located near a gene that influences the early onset of heart disease, supporting the hypothesis of a genetic basis for the condition.

Watch next

Master Mapping Genes with a bite sized video explanation from Kylia

Start learning

Related Videos

Related Practice

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.

453

views

Textbook Question

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

522

views

Textbook Question

A female of genotype

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?

732

views

Textbook Question

A genetic study of an early onset form of heart disease identifies 10 families containing members with the condition. No clear dominant or recessive pattern of inheritance is evident, but an analysis of SNP markers for five families detects a strong association with a marker on chromosome 12, and genetic linkage analysis for the marker produces a lod score of 2.2.

What next step do you recommend for this genetic analysis?

349

views

Textbook Question

In Drosophila, a female fly is heterozygous for three mutations, Bar eyes (B), miniature wings (m), and ebony body (e). Note that Bar is a dominant mutation. The fly is crossed to a male with normal eyes, miniature wings, and ebony body. The results of the cross are as follows.

111 miniature; 101 Bar, ebony

29 wild type; 31 Bar, miniature, ebony

117 Bar; 35 ebony

26 Bar, miniature; 115 miniature, ebony

Interpret the results of this cross. If you conclude that linkage is involved between any of the genes, determine the map distance(s) between them.

2343

views

Textbook Question

DNA sequences for 10 individuals are

Identify the haplotype carried by each person.

435

views