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:

                                    Theta (θ) Value
               0.01    0.05     0.10     0.20     0.30     0.40
SCA5    11.02   12.26   11.94   10.04    7.26     3.77
and
DNA
marker A

SCA5    0.35.    0.94.     1.07     0.99     0.75    0.43
and
DNA
marker B

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

Key Concepts

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 is due to the reduced likelihood of recombination occurring between them. In the context of the question, understanding linkage helps determine whether DNA marker B is associated with the SCA5 gene based on the lod score data provided.

Lod Score

A lod score (logarithm of the odds) is a statistical measure used to evaluate the likelihood of genetic linkage between a marker and a trait. A lod score greater than 3 suggests significant linkage, while a score below -2 indicates no linkage. The lod scores for DNA marker B in the study can be analyzed to assess its potential association with SCA5.

Theta (θ) Value

Theta (θ) value represents the recombination frequency between two genetic loci, indicating the probability that a crossover will occur between them during meiosis. Lower θ values suggest closer linkage, while higher values indicate greater distance. In the provided data, analyzing the θ values alongside the lod scores for DNA marker B is crucial for determining its linkage to the SCA5 gene.