Identical TwinsFrom Wikipedia The Free EncyclopediaJump
Identical twins
From Wikipedia, the free encyclopedia
Jump to: navigation, search
Identical twins start out as genetically identical: they have the same alleles. They are formed by a fertilised egg dividing into two separate individuals, and are always of the same sex. They may be calledmonozygotic or MZ twins (mono = one; zygote = fertilised egg). They contrast with fraternal twins, who are formed by two separate eggs fertilised by two separate sperms, and who are not always the same sex (DZ = dizygotic). Both types of twin are carried in the same uterus at the same time, so their birth environment is the same.
Research shows that the frequency of monozygotic twinning is one in 240 births. Fraternal twins are twice as common.[1]
Twin research[change | change source]
Identical twins are natural clones. Because they start out with the same genes, they can be used to investigate how much heredity contributes to individual people. This is the nature vs nurture question.Studies with twins have been quite interesting. If we make a list of characteristic traits, we find that they vary in how much they owe to heredity. For example:
Eye colour: entirely inherited.
Weight, height: partly inherited, partly environmental.
Which language you speak: entirely environmental.
The way the studies are done is like this.[2] Take a group of identical twins and a group of fraternal twins, and a group of siblings from the population. Measure them for various traits. Do a statistical analysis (such as analysis of variance). This tells you to what extent the trait is inherited. You will find that all those traits which are partly inherited will be significantly more similar in identical twins.Studies like this may be carried further, by comparing identical twins brought up together with identical twins brought up in different circumstances. That gives a handle on how much circumstances can alter the outcomes of genetically identical people.[3]The person who first did twin studies was
From Wikipedia, the free encyclopedia
Jump to: navigation, search
Identical twins start out as genetically identical: they have the same alleles. They are formed by a fertilised egg dividing into two separate individuals, and are always of the same sex. They may be calledmonozygotic or MZ twins (mono = one; zygote = fertilised egg). They contrast with fraternal twins, who are formed by two separate eggs fertilised by two separate sperms, and who are not always the same sex (DZ = dizygotic). Both types of twin are carried in the same uterus at the same time, so their birth environment is the same.
Research shows that the frequency of monozygotic twinning is one in 240 births. Fraternal twins are twice as common.[1]
Twin research[change | change source]
Identical twins are natural clones. Because they start out with the same genes, they can be used to investigate how much heredity contributes to individual people. This is the nature vs nurture question.Studies with twins have been quite interesting. If we make a list of characteristic traits, we find that they vary in how much they owe to heredity. For example:
Eye colour: entirely inherited.
Weight, height: partly inherited, partly environmental.
Which language you speak: entirely environmental.
The way the studies are done is like this.[2] Take a group of identical twins and a group of fraternal twins, and a group of siblings from the population. Measure them for various traits. Do a statistical analysis (such as analysis of variance). This tells you to what extent the trait is inherited. You will find that all those traits which are partly inherited will be significantly more similar in identical twins.Studies like this may be carried further, by comparing identical twins brought up together with identical twins brought up in different circumstances. That gives a handle on how much circumstances can alter the outcomes of genetically identical people.[3]The person who first did twin studies was