genetic epidemiology Genetic epidemiology is the study of the role of genetic factors in determining health and disease in families and in populations, and the interplay of such genetic factors with environmental factors. Genetic epidemiology seeks to derive a statist ...

, 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 Family aggregation, also known as familial aggregation, is the clustering of certain traits, behaviours, or disorders within a given family. Family aggregation may arise because of genetic or environmental similarities.Butcher, J., S. Mineka, and ...

for the disease or trait, in which having a

family history Genealogy () is the study of families, family history, and the tracing of their lineages. Genealogists use oral interviews, historical records, genetic analysis, and other records to obtain information about a family and to demonstrate kinsh ...

is associated with greater risk. The family research design can also be used to estimate

penetrance Penetrance in genetics is the proportion of individuals carrying a particular variant (or allele) of a gene (the genotype) that also express an associated trait (the phenotype). In medical genetics, the penetrance of a disease-causing mutation is ...

for a given

genotype The genotype of an organism is its complete set of genetic material. Genotype can also be used to refer to the alleles or variants an individual carries in a particular gene or genetic location. The number of alleles an individual can have in a ...

, to conduct

genetic association Genetic association is when one or more genotypes within a population co-occur with a phenotypic trait more often than would be expected by chance occurrence. Studies of genetic association aim to test whether single-locus alleles or genotype f ...

studies, and to study potential modifiers of an individual's genetic risk. 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.

Types

There are three main types of family studies in genetics: #Those aimed at measuring the extent of familial aggregation for a trait ##Familial aggregation is the practice of combing multiple data sets of different traits and/or characteristics in a family. ##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. #

Linkage studies Genetic linkage is the tendency of DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction. Two genetic markers that are physically near to each other are unlikely to be ...

aimed at identifying specific

genetic loci In genetics, a locus (plural loci) is a specific, fixed position on a chromosome where a particular gene or genetic marker is located. Each chromosome carries many genes, with each gene occupying a different position or locus; in humans, the total ...

that have a moderate to large effect on risk ##Genetic linkage occurs when two genes on a DNA sequence on the same chromosome are inherited together. ##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. #Association studies aimed at detecting loci with relatively small effects on risk. ##Locus (loci plural) is the physical location and position of a gene or genetic marker on the chromosome. ##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.

References

Genetic epidemiology {{Genetics-stub