People often confuse names and do not understand the differences between chromosomal syndromes and gene diseases. These terms refer to different pathologies. From this article you will learn what a karyotype is, what is the peculiarity of chromosomal diseases.
What does the term "karyotype" mean?
Karyotypes are certain combinations of chromosomes. Cytogenetic studies for their quantity and structure are carried out at any age, once in a lifetime. What can be determined from the chromosome in the study:
- Shape and size.
- Shoulder length.
- The presence of additional constrictions.
- The location of the telomeres.
Types of Karyotypes
All types of living organisms, including humans, have their own karyotypes. This is a combination of all the qualities of chromosomes, the composition of which ensures the normal functioning of each individual individual in the living world. A karyotype happens:
- Species, that is, characteristic only for this species.
- Individual - characteristic of an individual.
Normal human karyotype
Diseases that are accompanied by pathological changes are called chromosomal. Genetics studies their features and structure. Normally, human chromosomes (karyotype) consist of 46 pieces. There are two types in this composition. Sex chromosomes are contained in an amount of 2 pieces. The remaining 22 pairs are non-sexual, they are called "autosomes".
In women, sex chromosomes are represented by a pair of XX (two large chromosomes), and in men - XY (one large and one small). Based on this, the normal karyotype in the fair half of humanity has the formula 46XX, and in men - 46XY. Any deviations from these formulas cause various deformities, malformations, miscarriage, infertility, etc.
Karyotype Analysis
The analysis of the karyotype occurs at the stage of cell division, when their size changes. During this period, they are available for recognition. The study for karyotypes is carried out thanks to the method of special staining and the subsequent study of chromosomes in a light microscope. This method allows you to see the size and shape, structure of bodies, as well as primary or secondary constrictions and heterogeneity of the sites. For a visual description of chromosome changes, an international notation has been developed. First, their number is indicated (in numbers), then their type is noted - genital or autosomes, and the next record is features (mainly shoulder length).
All images in a microscope are photographed in order to record changes, and as a result of the totality of all frames, a complete picture is compiled. It is very important to pass tests for karyotypes, this will help to identify various pathologies even in the early stages of embryo development and development. After all, this affects the birth of healthy offspring.
Types of karyotype tests
There are 2 types of karyotype studies:
- Determination of the karyotype in leukocytes. This study is conducted by adults on the subject of finding or excluding chromosomal pathology. After all, if it is confirmed, then in future generations a genetic disease may appear . For such an analysis, the patient must donate blood for a karyotype.
- Prenatal study. This analysis is carried out in utero to determine the chromosomal pathology in the fetus. It is very important for future parents to do this analysis, check the karyotype. Although the price of it scares it off, it is necessary to find funds and do research. With some analysis results, abortion is indicated, as the fetal pathology may be incompatible with life or in the future will bring serious, irreparable consequences.
Who needs to take a karyotype test?
In many countries, karyotype testing is a prerequisite before marriage. And this is correct, because any person may experience a change in the structure of chromosomes, which does not affect his health. But this can only occur when planning a pregnancy.
As with any other test, there are relative and absolute indications for the definition. The first group includes:
- The presence of genetic pathology in one of the spouses.
- Permanent spontaneous miscarriages.
- Birth of a child with genetic pathology.
- The age of the future mother or woman planning a pregnancy is over 35 years old.
- The impact on the body of various pathogenic factors, such as radiation, chemicals, etc.
- Violation of sexual development.
Relative indications for karyotypes are optional predispositions. Analyzes in such cases should be taken.
What can I find out when taking a karyotype test?
After completing this study, you can learn a lot about your genetic health. The first and most pleasant thing is the belief that a person is healthy. Any change in the karyotype indicates abnormalities. This type of study will help to find out:
- Causes of various disorders in children, such as developmental delay, impaired intelligence, premature growth cessation, etc.
- Find out the risks of having offspring with genetic diseases.
In addition, this analysis allows you to recognize various chromosomal diseases. There are pronounced formulas, that is, karyotypes of syndromes, such as:
- Down Syndrome. This disease is formed inside the womb by 47 chromosomes. In 21 pairs, an additional unit is found, which is responsible for the disease.
- X chromosome polysomy.
- Patau Syndrome.
- Various vices.
- Cat Scream Syndrome , etc.
A karyotype with abnormalities is found in about 1% of all newborns. These disorders lead to mental retardation, various pathologies and even death. Cases of abnormalities increase with the age of the mother. This indicator affects the risk of developing Down syndrome in a child. In a pregnant woman under the age of 35, this risk is 1: 1000, up to 40 years -1: 200, and after 45 - 1:19.
Where can I do a karyotype test?
Despite the fact that this study is known and widely spread by many, some are wondering: where to take the karyotype and in what place do they take this analysis? This procedure is quite laborious and, accordingly, expensive, therefore, it is not carried out in district clinics. But in every big city there is an institution where an analysis for a karyotype is given, you just need to get a referral from your doctor. These organizations include:
- Family Planning Centers.
- Medical genetic institutions.
- Modern laboratories conducting various studies.
- Centers of motherhood and childhood.
- Private clinics.
To prevent an unfavorable outcome of pregnancy and identify the cause of infertility, you need to carefully study the chromosome set of both spouses. Modern detection of a violation of the karyotype allows the use of methods through which you can give birth to a healthy child.
One of the main reasons for changing the karyotype is the "wrong" spermatogenesis. Some sperm with impaired structure are involved in the fertilization of the egg. It is they that can cause the nucleation of an embryo with a modified karyotype. In addition, the appearance of disturbances is affected by the poor environmental situation, which provokes a mutation of chromosomes. And they, in turn, negatively affect the change in the human karyotype. These mutations are inherited, so you should not risk the health of your unborn child and neglect such analyzes.