Most often, twins are born in Africa, in Asian countries - less often. In Russia, the chance for twins is just over one percent. What does it depend on and whether it is possible to distinguish identical twins by DNA.
Diet + genes = twins
Scientists believe there is an inherited genetic predisposition to having twins. As geneticists from the UK have found out, multiple pregnancies may be associated with the IGF1 gene, more precisely the IGF-1 protein (insulin-like growth factor 1), which it encodes. This protein is involved in the regulation of the growth, development and differentiation of cells and tissues of the body. The authors of the work analyzed data on the weight of almost two thousand newborns - not twins. It turned out that those whose mothers ever gave birth to twins weighed more. If a single child was born after twins, on average, he was 226 grams heavier than other babies. Twins born earlier - by 134 grams. All mothers carrying twins had high IGF-1 levels. This protein is involved in the growth of the fetus and therefore affects the weight of the newborn. In addition, IGF-1 stimulates egg production in women, which contributes to multiple pregnancies. In a woman with a genetic predisposition to having twins, the chances of having twins are significantly increased with the right diet. According to the work of the American physician Gary Steinman, women who completely abandoned dairy products are five times less likely to give birth to twins than omnivores and vegetarians who consume milk.consuming milk.consuming milk.
It's again about insulin-like growth factor 1. Vegan women have much lower levels. These conclusions are indirectly confirmed by statistics - in countries where a lot of dairy products are traditionally consumed, twins tend to be larger.
Do not get out
Identical twins have the same set of genes, and it is almost impossible to distinguish between their biological samples (blood, saliva, hair) using conventional DNA analysis. This creates problems in the investigation of crimes. American forensic scientists solve this problem by developing a technique based on the analysis of epigenetic DNA methylation. Throughout life, small chemical marks (called epigenetic factors) appear on DNA. These are not mutations, they do not change the structure of the genome, but they affect the activity of certain genes in the cells and tissues of the body. These labels are the result of new habits, stressful experiences, and lifestyle changes. Scientists suggested that even identical twins should have different methylation patterns, and they were not mistaken. However, this technique has two significant drawbacks. It is impossible to distinguish biological samples of twins at a young age, since their epigenetic marks are very similar. The second problem is that the analysis requires about a hundred nanograms of DNA. Not always that much biomaterial is found at a crime scene.
Taste and color
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Wives and husbands of twins can be strikingly different in appearance and manners due to the fact that the choice of a life partner is not determined by genes, but by personal experience, American researchers have established. Biologists at Harvard University asked five hundred twins and about two hundred twins to take a computer test: to rate the beauty of two hundred images of human faces on a scale from one to seven. Individual aesthetic preferences of twins coincided only in half of the cases. Comparison of biographies and small details of the lives of the subjects showed that the tastes of the twins were most influenced not by general factors, but by minor differences - unique meetings, impressions, the appearance of the first lover or beloved, and other accidents. Scientists concluded that aesthetic preferences in choosing a life partner are completely determined by personal experience.
Support for loved ones and longevity
Under similar conditions, identical twins live on average longer than other people, according to researchers at the University of Washington. They analyzed data from nearly 3,000 pairs of monozygotic twins born between 1870 and 1900 in Denmark. The life expectancy of male twins was six percent longer than that of their peers. For female twins, this figure is even higher - ten percent. Scientists explained this by the fact that identical brothers and sisters support each other and help fight bad habits. Interestingly, mothers of twins also live longer. According to work biologists from the University of Utah, the life expectancy of women who bear and gave birth to twins is 7.6 percent higher than those who gave birth to one child or two children with a break of several years. The conclusion is based on an analysis of data from 60,000 Utah women who lived from 1807 to 1899 and had at least one child. Four and a half thousand of them were mothers of twins.
Alfiya Enikeeva