Family study

Types

There are three main types of family studies in genetics:

1. Those aimed at measuring the extent of familial aggregation for a trait
   1. Familial aggregation is the practice of combing multiple data sets of different traits and/or characteristics in a family.
   2. Family history of disease is collected in case studies, which seeks if a certain disease of one family member increases the risk of that disease being passed down to others. This could be related to either genes or environmental factors.
2. Linkage studies aimed at identifying specific genetic loci that have a moderate to large effect on risk
   1. Genetic linkage occurs when two genes on a DNA sequence on the same chromosome are inherited together.
   2. This can occur with sex linked genes with the X or Y chromosome. Although it is more common to be inherited from the X chromosome because the Y chromosome has less genes attached.
3. Association studies aimed at detecting loci with relatively small effects on risk.
   1. Locus (loci plural) is the physical location and position of a gene or genetic marker on the chromosome.
   2. Chromosomes carry genetic information across all of it, each gene having its specific location and position. There are 40,000 to 100,000 protein coding genes across human chromosomes.