In genetic epidemiology, family studies are studies of whether a disease or trait "runs in a family". In other words, they are studies aimed at detecting the presence or absence of familial aggregation for the disease or trait, in which having a family history is associated with greater risk. The family research design can also be used to estimate penetrance for a given genotype, to conduct genetic association studies, and to study potential modifiers of an individual's genetic risk.[1][2] If a family study shows that a trait is familial, this is a necessary, but not sufficient, criterion for it to be established as genetically influenced.[3]

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. [4]
    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.[5]
  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. [6]
    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. [7]
  3. Association studies aimed at detecting loci with relatively small effects on risk.[8]
    1. Locus (loci plural) is the physical location and position of a gene or genetic marker on the chromosome. [9]
    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. [10]

References

  1. ^ Roy, Alec; Rylander, Gunnar; Sarchiapone, Marco (December 1997). "Genetics of Suicide.: Family Studies and Molecular Genetics". Annals of the New York Academy of Sciences. 836 (1 Neurobiology): 135–157. doi:10.1111/j.1749-6632.1997.tb52358.x. ISSN 0077-8923. PMID 9616797. S2CID 29415906.
  2. ^ Hopper, John L.; Bishop, D. Timothy; Easton, Douglas F. (October 2005). "Population-based family studies in genetic epidemiology". Lancet. 366 (9494): 1397–1406. doi:10.1016/S0140-6736(05)67570-8. ISSN 1474-547X. PMID 16226618. S2CID 6434807.
  3. ^ Nestadt, Gerald; Samuels, Jack; Riddle, Mark; Bienvenu, O. Joseph; Liang, Kung-Yee; LaBuda, Michele; Walkup, John; Grados, Marco; Hoehn-Saric, Rudolf (2000-04-01). "A Family Study of Obsessive-compulsive Disorder". Archives of General Psychiatry. 57 (4): 358–63. doi:10.1001/archpsyc.57.4.358. ISSN 0003-990X. PMID 10768697.
  4. ^ "familial aggregation". TheFreeDictionary.com. Retrieved 2021-11-05.
  5. ^ Matthews, Abigail G.; Finkelstein, Dianne M.; Betensky, Rebecca A. (2008-10-30). "Analysis of familial aggregation studies with complex ascertainment schemes". Statistics in Medicine. 27 (24): 5076–5092. doi:10.1002/sim.3327. ISSN 0277-6715. PMC 2562890. PMID 18618413.
  6. ^ "linkage | Learn Science at Scitable". www.nature.com. Retrieved 2021-11-05.
  7. ^ "3.10: Genetic Linkage". Biology LibreTexts. 2016-09-21. Retrieved 2021-11-05.
  8. ^ "Family Studies in Genetics". Encyclopedia of Epidemiology. Thousand Oaks: SAGE Publications, Inc. 2008. doi:10.4135/9781412953948.n153. ISBN 9781412928168.
  9. ^ "Locus". Genome.gov. Retrieved 2021-11-05.
  10. ^ Ezkurdia, Iakes; Juan, David; Rodriguez, Jose Manuel; Frankish, Adam; Diekhans, Mark; Harrow, Jennifer; Vazquez, Jesus; Valencia, Alfonso; Tress, Michael L. (2014-11-15). "Multiple evidence strands suggest that there may be as few as 19 000 human protein-coding genes". Human Molecular Genetics. 23 (22): 5866–5878. doi:10.1093/hmg/ddu309. ISSN 0964-6906. PMC 4204768. PMID 24939910.


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