The methods of somatic cells genetics. The prenatal diagnostics of hereditary diseases

Such methods are based on studying cell culture of somatic cell. In a cell culture, the traits are expressed independently from environmental conditions and can be studied in clear state. Now using modem technologies, we can get generation line from one cell. It was stated that somatic cells may join together and form new cells. The cells from one organism as well as from other organisms may be joined. It results in hybrid formation. Hybrid cells have properties of precursor cells. They are used for studying immunological, biochemical, and cytological trait transmission.

The advantage of this method is getting genes in clear state, “per ce”. Also we can get as many cells as needed for cytological, biochemical and immunological analysis. In hybrid cells we can perform analysis of gene linkage and gene localization, discover mechanisms of gene activity, gene interactions, gene mutations and so on.

The molecular-genetic methods. The molecular-genetic methods help to describe changes in structure and functions of nucleic acids. Its include methods of gene extraction, gene synthesis, in vitro gene activity studying, gene transfection. It really pushed forward researches of human heredity and nature of hereditary diseases. Genetic engineering methods are real devices for treatment of hereditary diseases. It allows receiving primary human gene product and further using of it for patients with deficiency.

The reverse DNA transcription on mRNA matrix has resulted in discovering DNA probe. Such DNA probes facilitate localization of mutant genes in a cell. Further gene engineering development will result in new approaches for genetic diseases treatment.

The prenatal diagnostics of hereditary diseases. All methods of prenatal diagnostics can be divided to biological and physical. The physical methods are X-ray examination of embryo, ultrasonic examination and fetoscopia. X-ray examination gives diagnosis of hereditary defects only in last third of pregnancy. The anencephalia, spinal cord hernia and hydrocephaly are good visible in X-rays. The variant of X-ray examination is fetographia. This is a method when contrast substance is injected to amnion cavity.

This method allows diagnosing alimentary canal athresy, urinary system defects. The fetoscopy gives a real visible image of embryo, but it has many side effects and is used very rare. Many defects of nervous system are determined with help ultrasonic examination. Also it helps to evaluate defects of kidney such as polycystosis.

The biological methods are amniocentesis and chorionopexia (pic 10.8). The amniocentesis is performed on 14-1 б“1 week of development when amount of amniotic fluid is sufficient and when there is a time to cancel pregnancy. 15-20 ml of amniotic fluid are taken and centrifuged.

Pic. 10.8. The prenatal diagnostics of hereditary diseases: A - amniocentesis; В - chorionopexia (by F. Fogel, A. Motulsky, 1990)

The supernatant is used for biochemical and immunological methods, whereas cell detritus is used for cytogenetic methods. Now it is possible to determine sex of embryo, all chromosome abnormalities, more than 60 hereditary diseases, intolerance to Rh-antigen, hemoglobinopathy, enzymopathy, immunodeficiency syndromes with help of amniocentesis.

The same investigations are conducted while chorionopexia is performed. This method has several advantages over amniocentesis. It may be performed on earlier stage of development (6-7th week) and it excludes penetration of amniotic space. The material for investigation is chorion particles, taken from cervical canal of pregnant woman.

The human genetics value for medicine. The value of human genetics is huge. It gives methods of hereditary disease diagnostics. It is important not only in theoretical aspect for understanding evolutional and developmental processes, but also in practical too. It was calculated that among 5 billions Earth inhabitants, there are 10 millions which may be affected by different hereditary diseases such as diseases of nervous system (schizophrenia, epilepsy), endocrine system (cretinism), blood (hemophilia), metabolism (phenylketonuria, albinism) and so on.

The understanding causes of them allow treating them well. Using human genetics achievements, the genetic counseling service have been designed. The best worlds about human genetics value were said by I. P. Pavlov in 1935. “The life requires using of Mendel’s Laws of inheritance. The genetic principles have been studied enough to start using them intensively. Our doctors should know Laws of inheritance as ABC. The realization of knowledge about inheritance can relieve mankind from grief and sorrow.”