Question

A study is done on a group of families in Sweden that are segregating a genetic disorder. A statistical estimate of whether two genes, or a gene and a disease gene, are likely to be located near each other on a chromosome (called Lod-score analysis) indicates that the gene involved in the disorder shows a strong likelihood of linkage with a particular DNA marker locus. However, a second study done in Italy with other families segregating the same genetic disorder results in lod-score values that strongly indicate the lack of linkage between the gene and the same DNA marker locus. Assuming that both studies were performed appropriately, what is the most likely explanation for the different outcomes

Answer 1

Answer:

This disorder is caused by mutations in either of two different genes; one of these genes is linked to the DNA marker locus and the other gene is not.

Explanation:

A gene marker (also known as a molecular marker) is defined as a particular DNA sequence that has a specific physical location on a given chromosome. The gene markers are always physically linked with genes of interest, thereby they are useful for identifying patients affected by a given disease and/or a particular phenotypic trait. In this case, in the first study, genetic variation of the marker has been shown to be useful to map one locus that is associated with the disease phenotype. However, in the second study, a second locus that is not linked to the marker can segregate independently, thereby showing different results from the first study (in this case, it is imperative to develop a new genetic linkage analysis to discover genetic markers linked to the second gene, which is also responsible for the disease phenotype).