How often can we hear from future parents a phrase-question: "I wonder who our baby will look like?" Perhaps, he will have eyes like his father's, and sponges, like my mother's? ". Usually future parents do not rely on the basics of genetics, when they ask such questions, although they influence the similarity of the child with someone from adults. It is thanks to heredity that babies become like parents, but they never look like full copies of them. This is affected by the multiplicity and diversity of genes.
As soon as the baby is born, parents immediately try to determine who they look like, but it's still very early. Yes, he may already have some dominant trait, inherited from one or both parents, but at this age the kids change very quickly and acquire the features of one or the other parent, they are gradually recessive and dominant signs inherent in everyone. What are the dominant signs of a person?
Each person has 46 chromosomes, which arise when the sex cells completely merge. These chromosomes contain genetic information from each of the parents, and it becomes the basis of the future organism. The process of forming the genetic basis is very complicated, during it, in simple terms, all parental attributes are not only summed up, but then even divided equally. So whether your baby's eyes, like a mom or dad, depends more on the case. Here it is worth remembering the notion of a dominant feature. From the school course of biology, everyone knows that genes are divided into strong and weak. During their confrontation, a certain combination of characteristics is obtained.
The dominant features of a person are: a dark color of the eyes and hair, a large nose, full lips. If to speak easier - that all dark and big will prevail over light and small. That is, if the papa's eyes are brown, and his mother's are blue, then most likely the child will inherit the eye color from the father. But do not forget that recessive and dominant signs are not absolute indicators of future appearance. So, for example, if both parents have brown eyes, the child's eyes may be blue. And, according to the laws of genetics, the manifestation of recessive traits is observed in 25% of cases. In addition to the fact that there is a dominant feature, there is also heredity, which also affects the appearance of the child. Further, in adulthood, the appearance will already be determined not only by the genetic predisposition, but also by the external factors of man: nutrition, way of life.
If we try to trace how the dominant trait is inherited in several generations, then we can see that there is a certain pattern in its manifestation - in each generation this feature will be traced and must be present at one of the parents. Subsequently, it will manifest in half of the babies born. And if we talk about a recessive trait, then it will manifest itself in one generation, in the analysis of several, and the number of children it will be observed will be only a quarter.
Unfortunately, there are pathological hereditary signs that manifest themselves as a disease and can also be transmitted from parents to children as dominant. But due to mutations, these pathological signs can be completely excluded from the chain of genes, which will lead to the disappearance of "sick" genetic traits, and the child will not find a disease that has persecuted all relatives for many generations. In this case, the average frequency of all hereditary diseases still remains constant. This is due to the fact that because of the mixing of populations associated with population migration, the set of genes of each person is constantly updated. Together with the update there is a mutation.