Twins method (the study of twins).

Date: 2015-10-07; view: 595.

The study of twins is used to establish of heredity role and environment role in the genesis of one or another disease (character). The pairs of twins are examined. The twins are divided on dizygotic (dizygous) and monozygotic (monoovular, monochorial) twins. The monozygotic twins are twins that are generated from one impregnated ovule. The both of twins in the pair are genetically identical. If they live in different conditions, and each of them has different traits, this means the environment has big role in genesis of these traits.

The dizygotic twins are twins that are generated from two different impregnated ovules. The twins are genetically non-identical. . If they live in the same conditions, and each of them has different traits, this means the heredity has big role in genesis of these traits.

To take the more exact information of the heredity role and the environment role in the genesis disease (character) the mathematical methods are used.

The most known is Holecenger's formula:

H = %CMT - %CDT / 100% - %CDT

H – is ratio of heredity,

%CMT – is concordance percent of monozygotic twins.

%CDT – is concordance percent of dizygotic twins.

Concordance means a situation in which both of twins of pair have the same trait (disease).

Discordance means a situation in which each of twins of pair has the different traits (diseases). Or one of twins has disease, but other one is healthy.

The ratio of heredity can be changed from 0 to 1(or from 0% to 100%). If the ratio is less than 0,5 (or 50%), this means the influence of heredity has prevalence in the genesis of the trait (diseases). If the ratio is more than 0,5 (or 50%), this means the influence of environment has predominance in the genesis of the trait (diseases).