Identical twins that share 100% of their DNA. A result of an egg getting fertilised by two sperms at the same time and then splitting.
Dizygotic?
Non-identical twins that share 50% of their DNA. A result of two eggs getting fertilised at the same time.
Concordance rate?
If both twins develop a behaviour they’re said to be concordant.
If a behaviour is entirely genetic then MZ twins will have 100% concordance rate.
If a behaviour is environmental, then MZ twins and DZ twins show the same concordance rate.
Kray twins?
Identical brothers, gangsters and murders. They were perpetrators of organised crime in London from late 1950s to 1960s. Eventually arrested in 1968 and each was sentence to life.
Strengths of twin studies - natural experiments?
The biological relationship between twins is a naturally occurring variable.
Strengths of twin studies - Christiansen (1977)?
Studied 3500 twin pairs. Found a concordance rate of 35% in male MZ, compared to 13% in male DZ. This indicates a degree of inheritance.
