Hopes and fears about who the unborn child will look like, from which of the parents the intellect will inherit, and what character traits he will always have inherent in moms, dads, grandparents throughout pregnancy and during infancy. But not so much depends on the parents themselves - the chromosomal theory of heredity, genetics and ... the case work here.
It is known that human chromosomes containing genes are divided into two types - autosomes and sex chromosomes. Some genetic characteristics are related to human gender, while autosomes contain the rest of the hereditary information. A gene is a piece of DNA containing a series of nucleotides, the sequence of which is genetic information, which subsequently leads to the formation of specific characteristics of the body. They are of two types - dominant and recessive. The method of recording genetic information in genes, consisting of a nucleotide sequence, is called the genetic code.
Both eggs and sperm at the time of conception bring in their 23 pairs, which are necessary for determining the genetic code of the fetus. Even then, the eye color of the unborn child is laid, its physical structure, distinctive tendencies and inclinations. This magic number 23 means that both mother and father pass on only half of their genetic capital - something that cannot be predicted. That is, each characteristic of the child is the result of the crossing of the material of both parents. 22 autosomes are numbered by size. The other two chromosomes, X and Y, are sex chromosomes. This picture of human chromosomes is arranged in pairs and is called a karyotype.
Heredity, which plays an important role in the process of reproduction, is a fundamental property of living organisms and their characteristics - morphological, physiological, biochemical or psychological. The basic laws of heredity were formulated in 1866 by G. Mendel, who is considered the founder of the science of genetics. He said that individual properties, which depend on specific hereditary factors (later called genes), during the formation of gametes, divide and participate in their fertilization. As a result, people are born with various combinations of paternal and maternal genes.
The work of Mendel continued the American geneticist Thomas H. Morgan. His chromosome theory of heredity is based on the results of studies of Drosdophilus flies. He came to the conclusion that genes located on different chromosomes are inherited independently of each other. The fusion of chromosomes during fertilization is of great importance in the transfer of hereditary properties. Each pair contains similar genes, and the simplest forms of inheritance can be associated with one pair of genes.
In addition, the chromosome theory of heredity argues about possible disruption of gene linkage. Failures in the normal number of chromosomes in the cells are the main cause of human genetic diseases . Some chromosomal abnormalities do not cause disease in the host, although they are likely to lead to the birth of a child with an abnormal number of chromosomes (chromosomal syndrome). This pathology can be expressed in a reduced number of chromosomes, the presence of their copies, the opposite direction or the attachment of a part of the chromosome to another chromosome. Most mutations are fairly neutral and have no effect on human development. An exception is chromosome aberrations that alter the structure of chromosomes.
Morgan's research was not in vain. His chromosome theory of heredity has been confirmed and, most importantly, further developed in the study of the nature of the gene.