Twin study

Twin studies are studies conducted on identical or fraternal twins. They aim to reveal the importance of environmental and genetic influences for traits, phenotypes, and disorders. Twin research is considered a key tool in behavioral genetics and in content fields, from biology to psychology.

Overview

Twin studies are part of the broader methodology used in behavior genetics, which includes all data that are genetically informative — siblings studies, adoption studies, pedigree, etc. These studies have been used to track traits ranging from personal behavior to the way one may react to the environment.

Types of Twins

There are two types of twins: identical and fraternal. Identical twins share 100% of their DNA while fraternal twins share 50% of their DNA. The comparison of identical and fraternal twins can provide insights into the relative importance of genetic and environmental influences on particular traits.

Identical Twins

Identical twins or monozygotic twins occur when a single egg is fertilized to form one zygote which then divides into two separate embryos. They share the same genetic material and are always of the same sex.

Fraternal Twins

Fraternal twins or dizygotic twins occur when two separate eggs are fertilized by two separate sperm. They share 50% of their DNA and can be of the same sex or different sexes.

Twin Studies in Research

Twin studies are utilized in research for their unique genetic situation and can provide a great deal of insight into the genetic and environmental influences on behavior.

Behavioral Genetics

In behavioral genetics, researchers try to quantify the relative contributions of genetic and environmental factors to variation in phenotypic traits.

Epigenetics

Epigenetics refers to changes in gene expression that are stable between cell divisions, and sometimes between generations, but do not involve changes to the underlying DNA sequence. Twin studies help researchers understand the role of epigenetics in various diseases and conditions.

Criticisms

Despite the valuable insights that twin studies provide, they also face several criticisms. These include the equal environments assumption (EEA), the representativeness of twins, and the conflation of shared genes and shared environment.

See Also

• Genetics
• Behavioral genetics
• Epigenetics
• Identical twins
• Fraternal twins

References

Twin study Resources
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