Gemini (21 photos) Bashny.Net

Continue Cultural enlightenment.
Today on the agenda - the twins.

Twins - more children born at the same time from the same mother - twins, triplets and so on. N. There are identical (monozygotic) and fraternal (dizygotic) twins.

Monozygotic twins are formed from a single zygote, cleavage stage is divided into two (or more) parts. From a genetic point of view, they are identical, ie, They have identical genotypes. Monozygotic twins are always of the same sex.

Dizygotic twins develop in case simultaneously two eggs are fertilized by two sperm. Naturally, dizygotic twins have different genotypes. They resemble each other no more than brothers and sisters, because are about 50% identical genes. The overall incidence of multiple births is about 1%, of which about 1/3 accounts for monozygotic twins.

It is known that the number of births monozygotic twins is similar in different populations, while for the DZ this figure differs significantly. For example, in the United States dizygotic twins are born more common among blacks than whites. In Europe, the frequency of dizygotic twins is 8 per 1,000 births. However, in some of their populations is more. The lowest frequency of twin births is inherent in Mongoloid populations, especially in Japan.