Question

10. What factors contribute to a SNP/allelic marker having a higher level of significance in an association study? (4 pts)

11A. What is linkage disequilibrium (LD)? Give a concise definition. (3 pts)

11B. What does it mean for casual alleles to be in “perfect LD” with one of the SNPs being genotyped? (3 pts)

Answer 1

10. single nucleotide polymorphisms frequently called SNPs are most common type of genetic variationamong people.SNPs occur normally throughout a person's DNA.in association studies SNPs are typically used as markers,SNPs have typically 2 allels,meaning within a population there are two commonly occuring base pair possibilities for a SNP location.Researchers have found SNPs that may help predict an individual’s response to certain drugs, susceptibility to environmental factors such as toxins, and risk of developing particular diseases. SNPs can also be used to track the inheritance of disease genes within families.

11. A. LD means linkage disequilibrium is the non-random association of alleles at different loci in a given population. Loci are said to be in linkage disequilibrium when the frequency of association of their different alleles is higher or lower than what would be expected if the loci were independent and associated randomly.

11. B.The case of perfect LD happens if and only if the two SNPs have not been separated by recombination, but also have the same allele. LD is of importance in evolutionary biology and human genetics because so many factors affect it and are affected by it. LD provides information about past events and it constrains the potential response to both natural and artificial selection. it reflects reflects the population history, the breeding system and the pattern of geographic subdivision, whereas LD in each genomic region reflects the history of natural selection, gene conversion, mutation and other forces that cause gene-frequency evolution.