Question

A group of families in which an autosomal dominant condition is present are studied to determine lod scores for possible genetic linkage between three RFLP markers (R1, R2, and R3) and the disease gene. The chart shows lod scores at each of the recombination distances (0 values) tested RFLP θ values 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 R1 0.5 0.8 1.8 2.2 1.9 0.7 0.2 0.1 R2 1.1 3.1 3.8 3.0 2.1 1.0 0.8 0.1 R3 0.2 0.3 0.1 0.3 0.4 0.6 0.8 0.7

Answer 1

Results are inconclusive regarding linkage between the disease gene and R1 or R3 . The results provide strong support for genetic linkage between R2 and the disease gene with the most likely distance being 15 centiMorgan.

LOD score of more than 3 is considered to be 1000x more linked to the gene.Since LOD scores are calculated based on recombination frequency, R2 is the linked gene to disease gene at 0.15 recombination distance with LOD score of 3.8.