Karyotyping of peripheral blood lymphocytes of a couple. How and why karyotyping is carried out for expectant mothers and fathers - examination mechanism

The karyotype reflects the human chromosome set. Normally, a person has 46 chromosomes or 23 pairs. 23rd pair - sex chromosomes - XX in a woman, XY in a man. Karyotype analysis conducted for children and adults. The karyotype of the child allows to exclude some genetic diseases. Karyotyping of spouses helps to identify the genetic cause of infertility and miscarriage, as well as the prognosis of healthy offspring.

What is a karyotype?

Karyotype- a complete set of chromosomes in human cells. The norm for the content of chromosomes in somatic (non-embryonic) human cells is 46 chromosomes, organized into 23 pairs. Each pair consists of one chromosome from the mother and one from the father. To study the human karyotype, blood is taken from a vein. In the CIR Laboratory, karyotyping is carried out by cytogenetic and molecular genetic methods. There is also a FISH-analysis of the karyotype, which allows you to analyze chromosomes using fluorescent dyes.

The CIR laboratory performs the following karyotyping tests:

The first three analyzes are performed by the cytogenetic method. XMA is a molecular genetic analysis of a karyotype.

Let's talk about the cytogenetic method for performing karyotype analysis.
The appearance of chromosomes changes significantly during the cell cycle: during the interphase, chromosomes are localized in the nucleus, as a rule, despiralized and difficult to observe; therefore, cells in one of the stages of their division, the metaphase of mitosis, are used to determine the karyotype. Chromosomes in a light microscope at the metaphase stage are DNA molecules packed with the help of special proteins into dense, supercoiled rod-shaped structures. Thus, a large number of chromosomes are packed into a small volume and placed in a relatively small volume of the cell nucleus. The location of the chromosomes, visible under a microscope, is photographed and a systematized karyotype is collected from several photographs - a numbered set of chromosome pairs of homologous chromosomes. In this case, the images of chromosomes are oriented vertically, with short arms up, and their numbering is carried out in descending order of size. A pair of sex chromosomes (X and Y for a man, X and X for a woman) are placed at the very end of the image of the set of chromosomes.

When is blood donated for karyotype?

An examination for a karyotype is a non-routine analysis, for which there are indications.

Reasons a doctor may suggest testing may include:

the birth of a child with a genetic pathology or the presence of a chromosomal pathology in relatives of one of the spouses;
infertility in the family;
habitual miscarriage and / or spontaneous miscarriage in the first 12 weeks of pregnancy;
exposure to radiation, harmful production at work, etc.

What to pass the analysis on a karyotype?

Karyotype analysis can be performed in two ways: karyotyping without aberrations and karyotyping with aberrations. The first analysis shows the genetic set of a person - the number of chromosomes and large changes in all chromosomes received from parents. Karyotyping with aberrations shows changes that occur in chromosomes during a person's life under the influence of various harmful environmental factors. An analysis for a karyotype by the CMA method is handed over in rare cases with growth retardation in children, autism, suspicion of microdeletion syndromes.

Analysis of the karyotype of a married couple (karyotyping of spouses)

To identify a possible cause of infertility in the family, the doctor may prescribe karyotyping to spouses. Spouses can take the test at different times, this does not affect the interpretation. If there is an assumption about the genetic nature of infertility, a karyotype analysis can be assigned to one of the spouses. .

How to take a karyotype test? Where can I take a karyotype test?

Karyotype: price of analysis

Find out the price of karyotype analysis in our price list,.

Karyotype analysis: how is a human karyotype study performed?

Each chromosome consists of specialized structures - a centromere and two telomeres. The centromere (cen) or primary screed divides the chromosome into two parts - long (q) and short (p) arms and is responsible for the separation of chromosomes during cell division. Prior to cell division, a chromosome consists of a single chromatid. After duplication of DNA - from two chromatids, until they separate into two new cells.

For the procedure for determining the karyotype cytogenetic method any population of dividing cells can be used. To determine the human karyotype, as a rule, peripheral blood lymphocytes are used. To analyze the karyotype, blood is taken from a vein into a sterile test tube. There are no conditions for taking the analysis; you can have breakfast before visiting the laboratory.

The transition of lymphocytes from the G0 resting stage to proliferation is provoked by the addition of a cell division stimulator - phytohemagglutinin. Bone marrow cells or a primary culture of skin fibroblasts can also be used to determine the karyotype. To increase the number of cells at the metaphase stage, shortly before fixation, colchicine or nocadazole are added to the cell culture, which block the formation of microtubules, thereby preventing the chromatids from spreading to the poles of cell division and the completion of mitosis.

After fixation, preparations of metaphase chromosomes are stained and examined under a microscope.

To obtain a classical karyotype, chromosome staining with various dyes or their mixtures is used: due to differences in the binding of the dye to different parts of the chromosomes, staining occurs unevenly and a characteristic banded structure (a complex of transverse marks, English banding) is formed, reflecting the linear heterogeneity of the chromosome and specific for homologous pairs chromosomes and their sections (with the exception of polymorphic regions, various allelic variants of genes are localized). The first chromosome staining method to obtain such highly detailed images was developed by the Swedish cytologist Kaspersson (Q-staining). \\Other dyes are also used, such techniques are collectively called differential staining of chromosomes.

Types of differential staining of chromosomes

G-staining- modified staining according to Romanovsky - Giemsa. The sensitivity is higher than that of Q-staining, therefore it is used as a standard method for cytogenetic analysis. It is used to detect small aberrations and marker chromosomes (segmented differently than normal homologous chromosomes).

Q-staining- staining according to Kaspersson with acrichin mustard with a study under a fluorescent microscope. Most often used to study Y chromosomes (quick determination of genetic sex, detection of translocations between X and Y chromosomes or between Y chromosome and autosomes, screening for mosaicism involving Y chromosomes).

R-staining- acridine orange and similar dyes are used, while staining parts of the chromosomes that are insensitive to G-staining. Used to reveal details of homologous G- or Q-negative regions of sister chromatids or homologous chromosomes.

C-staining- used to analyze the centromeric regions of chromosomes containing constitutive heterochromatin and the variable distal part of the Y chromosome.

T-staining- used to analyze telomeric regions of chromosomes.

Chromosomal microarray analysis (CMA)

More modern technology for studying the karyotype. Karyotype analysis is performed by the molecular genetic method aCGH (comparative microarray genomic hybridization), which, unlike the classical cytogenetic method, has a high resolution that allows detecting smaller structural changes in the karyotype.

Fluorescence in situ hybridization Fluorescence in situ hybridization, FISH

Detection of aneuploidy - violation of the number of chromosomes. In the image, green corresponds to chromosome 13, and red corresponds to chromosome 21, which indicates the presence of triploidy on chromosome 21 in this sample.

Recently, the technique of the so-called spectral karyotyping (fluorescence in situ hybridization, English Fluorescence in situ hybridization, FISH) has been used, which consists in staining chromosomes with a set of fluorescent dyes that bind to specific regions of chromosomes. As a result of such staining, homologous pairs of chromosomes acquire identical spectral characteristics, which not only greatly facilitates the identification of such pairs, but also facilitates the detection of interchromosomal translocations, that is, movements of sections between chromosomes - translocated sections have a spectrum that differs from the spectrum of the rest of the chromosome.

Violations in the structure of chromosomes may not manifest themselves in any way during life. But when the egg and sperm merge, two genetic sets meet, and then an unsuccessful match of genes can cause a miscarriage or the formation of a congenital pathology in the fetus. Karyotyping of spouses helps to identify abnormalities in the structure and number of chromosomes, as well as the likelihood of a particular deviation.

Karyotype examination is an optional analysis. The procedure has its own indications, including miscarriages and missed pregnancy in history. Reproductive problems associated with the peculiarities of genetics are quite rare.

Karyotyping is a diagnostic procedure that detects abnormalities in the structure and number of chromosomes. Such deviations can cause hereditary pathologies in a child and infertility of spouses.

Each person has their own specific set of genes, which is called a karyotype. Chromosomes are arranged in pairs: 22 pairs of autosomes and 1 pair of sex chromosomes, which are represented as XX in the female body, and XY in the male body. They consist of genes - sections that are responsible for the manifestation of a particular trait.

Karyotyping detects diseases that are directly related to changes in DNA. The defect can be in any gene, in the structure of chromosomes or their number. The most famous example is Down syndrome, also called trisomy 21.

Karyotyping of spouses (cytogenetic analysis) is a study of the chromosomes of blood cells. The procedure reveals the causes of miscarriage or infertility in couples when other factors are already excluded (hormonal, immune, infectious). If increased genome instability is detected, the use of antioxidants and immunomodulators will help reduce the risk of conception failures.

Which couples are indicated for karyotyping?

As already noted, karyotyping of spouses is not included in the list of mandatory diagnostic procedures. It is shown in the following cases:

One or both parents are over 35 years old.
Infertility, the causes of which cannot be determined by other methods.
Several unsuccessful IVF procedures.
Living in areas with poor environmental conditions, working in hazardous industries, contact with hazardous chemicals.
Smoking, alcohol abuse, taking drugs, certain medications.
Previous miscarriages, miscarriages, premature births.
The spouses are blood relatives.
Previously born children with genetic diseases.

Preparation for the examination procedure

The analysis is carried out in a laboratory and does not pose any danger to the health of the spouses. 2 weeks before the procedure, you must stop drinking alcohol, tobacco products and medications. If the intake of any medication cannot be canceled, the laboratory assistant must be warned about this.

Blood sampling is carried out on a full stomach, the last meal should occur 1-2 hours before the analysis. Before the procedure itself, you need to fill out a special questionnaire or bring it with you (in some cases, it is filled out by the doctor in advance). If the karyotyping of spouses coincided with an exacerbation or acute course of an infectious disease in one or both of the couple, then the study should be rescheduled.

Conducting an analysis

In karyotyping, blood is taken from a vein. The laboratory assistant fills a test tube with it and releases the patient. It usually takes about 5 days for genetic analysis and preparation of results.

For further research, only a part of the material is needed - lymphocytes. They are isolated from the blood during the period of division. In order to provoke the activity of this process, special drugs are added (Colchicine, Nocazadol). Over the next three days, the features of cell reproduction are analyzed. Based on the results obtained, a conclusion is made about possible pathologies and risks of abortion.

Modern technologies allow karyotyping using only 15 cells and special preparations. Therefore, one blood sampling is enough to obtain accurate and complete information about chromosomes and genes.

What will result?

Interpretation of the analysis for karyotyping of spouses is carried out by a geneticist. The normal result for women is 46XX, for men - 46XY. It means that a total of 46 chromosomes were found, the last pair of which is sexual. When a genetic pathology is detected, this formula changes. For example, with Down syndrome (trisomy on chromosome 21), it looks like 46XX21+.

The result of karyotyping helps to determine the following pathologies:

Trisomy is the presence of an extra third chromosome in a pair. Trisomy on the 21st chromosome - Down syndrome, on the 16th - spontaneous miscarriage in the 1st trimester, on the 13th - Patau syndrome, on the 18th - Edwards syndrome. Of these, the only viable option is Down syndrome.
Monosomy is the absence of one chromosome from a pair. Monosomy of any autosomal chromosome leads to early death of the embryo. A similar pathology in couple XX in women is manifested by Shereshevsky-Turner syndrome.
A deletion is the absence of a part of a chromosome. If large areas are lost, early death of the embryo occurs. In other cases, genetic pathologies (for example, crying cat syndrome with a deletion of the 5th chromosome) or a positive effect on viability (for example, HIV resistance) may develop. Deletion of the sex chromosome in men is the cause of impaired spermatogenesis and leads to infertility.
A duplication is the presence of a duplicate fragment of a chromosome. The functions of the original genes are not affected.
An inversion is a 180° rotation of a part of a chromosome. Some of these changes are normal, while others lead to the death of germ cells and the formation of unbalanced material in them. The result is reduced fertility, increased risk of miscarriage and fetal abnormalities.
Translocation is the movement of a segment of a chromosome. Some of these changes do not affect the person in any way, the other leads to miscarriages, congenital fetal anomalies (Robertsonian translocations).

The results form records changes in the structure of chromosomes. The long shoulder is denoted by the letter "q", the short one - "t". For example, cat's cry syndrome (deletion on the 5th chromosome) is written as follows: 46XX5t or 46XY5t.

The second thing that is found during karyotyping is changes in genes. Can be identified:

Gene mutations that affect blood clotting. Increased thrombus formation can cause miscarriage, infertility, or the inability to implant a fertilized egg.
Mutation of genes in the Y chromosome is the cause of male infertility, requiring the use of donor sperm.
Gene mutations that reduce the body's ability to detoxify - get rid of harmful substances obtained from the external environment.
Changes in the gene for cystic fibrosis, leading to the occurrence of this disease in a child.

Identified deviations from the norm: what to do?

To obtain complete information about the results of karyotyping, the spouses need to come for a consultation with a geneticist. He will tell you in detail about the possible risks and the likelihood of developing a particular violation.

Karyotyping is one of the new methods of cytogenetic research, through which sets of human chromosomes (the so-called karyotype) are studied. Scientists, conducting their studies, can determine the structure of chromosomes and, if this is the case, a violation in their structure. Karyotyping of chromosomes is enough to carry out once in a lifetime - the results of the study determine the genome of the male and female individuals for correspondence to each other. In other words, thanks to such analyzes, it is possible to check whether a man and a woman match at the gene level, whether they can have children and whether their baby will be healthy.

The method of karyotyping is the latest proposal in medicine, which, nevertheless, is becoming more and more popular every year among young (and not very young) spouses.

A karyotype is a complete set of chromosomes, moreover, with a description of certain features - whether it be size, shape, quantity. In humans, as is known from the course of elementary biology, there are 46 chromosomes in the genome - a total of 23 pairs. At the same time, 44 chromosomes are autosomal: they are responsible for the transmission of data that denote hereditary traits of one kind or another. This includes the color and type of hair, the structure of the ears, the quality of vision, etc. But one pair of chromosomes is responsible for sexual characteristics - it is she who gives the female (“XX”) or male (“XY”) karyotype.

Thanks to the decoding of chromosomes, their comparison and connection, scientists can say with an accuracy of 99% about the probability of the birth of a handicapped or sick baby.

Molecular karyotyping: indications

Of course, it would be absolutely correct if absolutely all parents carry out karyotyping before having children. Moreover, regardless of whether doctors prescribe such an analysis or not. Perhaps in the future, such analyzes will be mandatory, but not today. So far, they are sent for karyotyping only if there are good reasons for this.

A number of hereditary diseases that occurred in the genus in a particular person sometimes appear quite unexpectedly (although predictably). Several generations can be absolutely healthy, and then some disease suddenly appears. It is karyotyping that can reveal the very pathology in the unborn child and calculate in advance all the risks.

An analysis is required if:

One or both spouses who decide to have a child are over 35 years old.
A woman cannot get pregnant for a long time, and doctors cannot determine the origin of infertility.
There were repeated attempts to carry out artificial insemination, but they were all unsuccessful.
One of the spouses in the family had some hereditary diseases.
The woman has some disorders, an imbalance of hormones in the body.
The man has a history of impaired spermatogenesis, and the cause of impaired sperm formation has not been established.
One of the spouses was in contact with hazardous chemicals.
One of the spouses received radioactive exposure.
Spouses live in an unfavorable ecological environment.
In the past, there were moments that could negatively affect the child. For example, earlier a woman or a man smoked, drank alcohol or drugs, took a lot of medicines.
A woman had three or more pregnancies terminated spontaneously (miscarriage, miscarriage, premature birth).
Man and woman are closely related.
The spouses already have a child with some kind of congenital pathology and malformation.

It is best to undergo karyotyping during pregnancy planning. But now there is an opportunity to examine the karyotype of the baby that the woman is carrying - the so-called prenatal karyotyping is carried out.

Karyotyping: preparation for analysis

To determine the karyotype, blood cells are needed. In order for the analysis to be more accurate and of high quality, everything possible must be done in order to exclude factors that complicate cell growth. That is why preparation for karyotyping often takes two or more weeks.

If you decide to check your karyotype, you need at least 14 days:

Do not smoke.
Do not drink alcoholic beverages.
Do not take medication (this primarily applies to antibiotics).
Do not get sick (this applies to both infectious colds and exacerbations of various chronic diseases).

Karyotyping: how to take

To identify a person's karyotype, venous blood is needed, which is taken from a man and a woman (it is very important that both spouses are ready for testing).
Having received venous blood, lymphocytes are screened out in the laboratory (they are just in a state of division (mitosis phase)).
To conduct a qualitative analysis, from 12 to 15 lymphocytes is quite enough - this is enough to identify quantitative and qualitative mismatches of chromosomes - they are the ones that indicate the presence of any genetic hereditary diseases.
For three days, lymphocyte cells are monitored - an analysis is made of their division, growth and reproduction.
To stimulate the phase of mitosis, lymphocyte cells are treated with a special compound - a mitogen.
When the direct process of division occurs, scientists study the chromosomes - in this case, mitosis should be stopped by a special treatment.
Once scientists have collected enough data, they prepare special preparations to study chromosomes on glass.
In order for the structure of chromosomes to be clearer, it is possible to add dye, which allows the genome to acquire color. Since chromosomes have individuality, after coloring they are able to become even more noticeable.
At the final stage, the stained smears are analyzed, which is able to determine not only the total number of chromosomes, but also the structure of each separately.
Comparing paired chromosomes and their striation, scientists check the result with their table, where the norms of cytogenetic schemes of chromosomes are written.

Karyotyping: results

An analysis for the study of the karyotype must be taken in a specialized clinic by a geneticist. If you are offered to undergo tests in a regular hospital, then there is a risk that the analysis will be unreliable, since most often in ordinary medical institutions there are no qualified doctors and devices to perform the process itself.

If the analysis is normal, then it should look like "46XX" (female) or "46XY" (male). In the event that experts suddenly discover a genetic disorder, the record will be more complicated. For example, “46XY21+” means that a man has a pathology in the form of an extra chromosome (moreover, 21 means that 21 pairs have the third chromosome).

Thanks to karyotyping, pathologies such as:

trisomy - the presence of a third extra chromosome in a pair (probably Down's syndrome);
monosomy - the absence of one chromosome in a pair;
deletion - the loss of some part of the chromosome;
duplication - doubling of one of the fragments of the chromosome;
inversion - an incorrect turn of some part of the chromosome;
translocation - castling of certain sections of the chromosome.

If a deletion is found in the Y chromosome, then this most likely indicates a violation of spermatogenesis and, as a result, infertility in a man. In addition, it is the deletion that is most often the cause of congenital pathology in a child.

To make it convenient, if there are any violations in the structure of chromosomes, scientists record the results of analyzes using Latin letters. For example: the long shoulder is designated "q", the short one - "t". If a woman has a history of loss of a fragment, say, the short arm of the fifth chromosome, then the entry will be like this - “46XX5t”. This genetic deviation is called "cat's cry" - a baby born to such a couple will most likely have congenital disorders, he will also cry for no reason.

Thanks to karyotyping, it is possible to assess the state of genes, since it is possible to identify:

A gene mutation that affects blood clots - this significantly disrupts blood flow and can cause miscarriage or even infertility.
Gene mutation of the Y-chromosome - pregnancy is possible, but only if there is another sperm (using a donor).
Mutation of the genes that are responsible for detoxification - this indicates that the body has a low ability to decontaminate toxic factors.
A gene mutation that is expressed in cystic fibrosis, which will help eliminate the risk of developing this disease altogether.

Modern equipment also makes it possible to identify predisposition to such diseases that do not have such a bright genetic characteristic: heart attack or diabetes mellitus, hypertension or joint pathology, etc.

Karyotyping: what to do next

If any abnormalities were found during karyotyping, the doctor will immediately inform the spouses about this. It doesn’t matter if it’s a gene mutation or a chromosomal aberration, for one or both spouses at once, the geneticist will explain everything in detail and clarify what the risks are for the unborn baby, how likely the birth of a sick child is.
It should be noted right away that a genetic pathology is incurable, if there are chromosome disorders, then the spouses must make a very important and responsible decision: still give birth to their child (at their own peril and risk), use donor sperm (egg), attract a surrogate mother, not to have a baby, but to adopt a baby.
If doctors have detected chromosome anomalies in a woman during pregnancy, doctors explain that there is a possibility of having a sick child and advise to terminate the pregnancy. But it is up to future parents to decide whether to have an abortion or not. No one has the right to insist on termination of pregnancy - neither a doctor, nor a geneticist, nor any of the relatives.
In the event that an anomaly of the chromosome number is in doubt or its presence gives a low percentage of the birth of a sick baby, then doctors prescribe a course of vitamins that reduce the likelihood of a baby being born with pathologies or abnormalities.

Fetal karyotyping: what is it?

If for a number of reasons parents did not perform karyotyping during pregnancy planning and a new life is already ripening under the woman’s heart, then perinatal karyotyping can be performed. This method will help to identify the presence of chromosomal pathologies in the fetus already in the first trimester of pregnancy. This study will identify any abnormalities and guide physicians for treatment, adjustment, or other unpopular actions needed during pregnancy.

Thanks to this method, it is possible to exclude Down syndrome, Patau, Turner, Edwards and Klinefelter, as well as X-chromosome polysomy.

Fetal karyotyping: methods

Currently, there are two methods that are used to conduct a study of the fetus.

non-invasive method. Completely safe for both mom and baby. For this study, it is enough to conduct an ultrasound examination, on which measurements of the fetus will be made, as well as a study of the biochemical analysis of the pregnant woman in order to identify special markers.
invasive method. A more serious method, since manipulations must be carried out directly in the uterus to detect pathology. The doctor takes either cells from the chorion or cells from the placenta for analysis, as well as cord blood and a sample of amniotic fluid. This analysis is more accurate. Thanks to a biopsy of the above materials, doctors can get enough information about the health of the baby. The whole procedure is performed in exactly the same way as described above - the human karyotype is determined by studying the chromosome set.

Fetal karyotyping: complications

Before practicing the invasive method of fetal karyotyping, the doctor must report that there is a small (no more than 2-3%) risk of complications after the studies. In the worst case, a miscarriage is possible, bleeding may occur, or amniotic fluid may begin to leak.

That is why before deciding on this procedure, it is necessary to weigh all the pros and cons and only then give your consent. If you just want to find out the sex of the child at an early stage (and with this method it is quite possible), it is better to refuse invasive karyotyping of the fetus. It is a completely different question if there is a risk of having a child with genetic abnormalities or anomalies.

Fetal karyotyping: indications

Intervention during pregnancy to carry out invasive karyotyping of the fetus is practiced only for medical reasons. This procedure is recommended if:

Pregnant for over 35 years and this is her first child.
Ultrasound examination showed the presence of pathology in the fetus.
In the blood of a pregnant woman, biochemical parameters - blood markers (AFP, hCG, PPAR) have changed dramatically.
There is a disease in the family that is transmitted only by gender (for example, hemophilia - this disease will be transmitted from a woman to her son, and not to her daughter).
The family already has a child with a pathology or malformation, or with a genetic disease.
A woman has miscarriages over long periods, as the fetus develops a developmental anomaly incompatible with life.
The child's parents were irradiated or worked for a long time (work) in a hazardous industry.
A pregnant woman in the first trimester suffered a viral disease.
One or both parents used drugs.

What is karyotyping. Video

Karyotype analysis is a modern laboratory test that allows you to identify possible pathological disorders at the genetic level, determine the cause of infertility and even determine whether the unborn child will be healthy. In the result obtained, changes in the set of chromosomes are recorded. The diagnostic procedure is currently in great demand because it allows establish the level of genetic matching of men and women.

Karyotype - chromosome set distinguished by certain characteristics. The norm is the presence of 46 chromosomes:

44 - responsible for similarity with parents (eye color, hair, etc.).
2 - indicate gender.

An analysis for karyotyping is necessary to determine the pathological disorders occurring in the body. Laboratory diagnostics is indispensable for establishing the causes of infertility and the presence of congenital pathologies that can be inherited.

The sequence of karyotyping:

Sampling of venous blood and screening of single-nuclear leukocytes in the laboratory.
Placement of biological material in a medium with PHA (phytohemagglutinin) and the beginning of cell cultivation (mitotic division).
Termination of mitosis after reaching the stage of metaphase, which is carried out with the help of colchicine.
Treatment with a hypotonic type solution and preparation of micropreparations.
Studying and photographing the formed cells with a special microscope.

Only after 2 weeks, specialists in the laboratory receive the result of the study. The form contains information on the total number of chromosomes, and the existing violations of the genetic code are recorded.

A genetic study is prescribed to assess the reproductive functions of a couple planning children. A complete picture of genetic features is needed to make a diagnosis. Based on the results obtained, it is possible to look for ways to solve the existing problem, if any. Karyotyping is aimed at determining the number, shape and size of chromosomes in a biological sample.

If there are any violations, there are problems from the internal systems and organs. In some cases, completely healthy people are carriers of a genetic mutation. It is not possible to determine this visually. As a result, problems with conception, malformations or the birth of an unhealthy child.

There are following medical indications for karyotyping:

age limit of 35 years and older;
abortion and infertility;
hormonal disorders in the female body;
exposure to or poisoning with chemicals;
polluted environment and the presence of bad habits;
hereditary predisposition and blood marriages;
the presence of a chromosome mutation in previous children.

A blood test for a karyotype should be performed once, because these characteristics do not change with age. An absolute indication for karyotyping is the problem of conception and the inability to endure pregnancy. In recent years, more and more young couples are undergoing this analysis in order to make sure that healthy children are born. Laboratory diagnostics makes it possible to assess the likelihood of a baby being born with abnormalities caused by a violation of the chromosomes and to identify the true cause of infertility.

Preparation for karyotyping

Blood cells are used for karyotyping, therefore, before passing the analysis, you need to prepare, eliminating the influence of third-party factors that complicate their growth. Otherwise, the study will be low informative.

Preparation must begin 2 weeks in advance:

Avoid alcohol, smoking and unhealthy foods.
Discuss stopping medication with your doctor.
9-11 hours before the sampling of biological material, exclude meals.
Do not drink liquids 2-3 hours before the laboratory test.

Blood donation for karyotype is carried out in the morning on an empty stomach. In the event of a deterioration in health, an infectious disease or an exacerbation of chronic diseases, the study is postponed until the patient recovers.

Aneuploidy (change in quantity). With poor-quality biological material, difficulties may arise in the diagnostic process.
Structural deviations - connected combinations after separation. The study reveals major violations. In order to identify minor deviations, a microarray chromosomal analysis is prescribed.

Types of diagnostics

Karyotyping is carried out in several ways, which differ in the approach to research and sources of biological material:

Classical- venous blood (10-20 ml) is taken for research. In pregnant women, amniotic fluid sampling may be required for diagnosis. In some cases, cells are taken from the bone marrow. Chromosomes are stained and examined by light microscopy.
SKY (spectral)- a new technique, which is considered the most effective, because it allows you to visually and quickly identify violations. In this case, parts of the chromosomes are detected using fluorescent labels without cell culture. It is used when standard karyotyping has failed.
FISH analysis (fluorescent hybridization)- the study is carried out in a special way and involves the specific binding of certain sections of chromosomes and fluorescent labels. For laboratory diagnostics, embryonic cells or ejaculate are taken.

To obtain the most accurate result, a blood test is carried out in conjunction with other, no less informative, genetic tests.

How to decrypt

A geneticist is engaged in making a diagnosis against the background of the result of karyotyping. The specialist conducts a thorough analysis and makes a conclusion in which he indicates the causes of violations of the reproductive functions or the birth of an unhealthy child.

Deciphering the analysis allows you to determine the following genetic disorders:

the presence of genetically different cells;
movement of sections of the genetic code;
reversal or duplication of the chromosome;
the absence of one fragment or the presence of an extra one.

With the help of karyotyping, it is possible to establish a predisposition to the development of hypertension, arthritis, myocardial infarction, stroke, and diabetes mellitus. Thanks to this analysis, thousands of couples have identified the cause of infertility and successfully cured of existing disorders in the body.

Deviations are possible both from the side of the male and from the side of the female body. Normal indicators:

in men - 46XY;
in women - 46XX.

In children, the following violations of the genetic code are observed:

47XX + 21 or 47XY + 21 - Down syndrome (presence of an extra chromosome).
47XX + 13 or 47XY + 13 - Patau's syndrome.

There are other deviations from the norm, which are less dangerous. Only a geneticist can account for the risks of an unhealthy child for each individual case. If dangerous disorders or mutations were found during karyotyping, the doctor recommends termination of pregnancy.

Karyotyping gives an assessment not only of the number, but also of the state of genes:

Mutations that cause thrombus formation, disrupting the nutrition of small vessels at the time of placental formation, which is the cause of miscarriages.
Pathologies from the cystic fibrosis gene, in order to exclude the likelihood of developing a certain disease in a child.
Gene disorders from the Y-chromosome.
Deviations from the genes that are responsible for the ability to decontaminate toxic factors.

When a deletion (loss of a site) is detected in the Y chromosome, we are talking about male infertility due to impaired spermatogenesis. This is the cause of hereditary diseases.

What to do if deviations are found

To exclude the possibility of genetic abnormalities in a child, it is necessary to check the karyotype of both parents even before conception. In the presence of genetic disorders, the doctor will explain the possible risks. Do not panic when detecting chromosomal mutations. Even in this case, it is possible to bear the pregnancy and give birth to a healthy child if a child is found, following the recommendations of the doctor.

Planning a child allows you to prepare the body of the mother and father for the birth of healthy offspring and determine the risks of having unhealthy children. Even after a woman has become pregnant, karyotyping can be done in the first week to assess possible risks, which allows timely measures to be taken to prevent miscarriage. In the presence of serious genetic mutations, the decision to terminate the pregnancy is made by the couple. The doctor only indicates the possible consequences and makes recommendations if interruption is necessary.

Conclusion

Genetics is now a failing developed scientific branch. With the help of modern diagnostic tests, it is possible to identify ongoing deviations in the initial forms of progression and take measures to combat them. Thanks to karyotyping, it is possible to cure infertility, prevent recurrent miscarriages, and eliminate the chance of having children with a genetic mutation. When planning a family, it will not be superfluous to check for genetic compatibility.

Often, deviations in development and difficulties with conceiving a child are associated with disorders that are inherited. If one of the parents has relatives suffering from genetic diseases, or he himself is a carrier, it is advisable to undergo an examination before planning the birth of a baby. Doctors take an analysis for a karyotype if they suspect a pathology of chromosomes or DNA molecules. For the study, blood is taken from the patient and treated with a coloring composition. After processing under a microscope, the size, shape and number of chromosomes are studied.

Definition

A karyotype is an individual set of chromosomes that has its own characteristics for each specific biological species and individual. A person has only 23 pairs of chromosomes, that is, a total of 46. Of the twenty-three pairs, only one determines sex, and the rest do not have differences in structure. Genetic analysis of the karyotype allows you to identify deviations in the composition or structure of chromosomes. Thanks to this study, doctors can take timely measures so that the pathology does not cause serious complications, up to the death of the fetus.

Important! It is enough for future parents to do karyotyping once in a lifetime to make sure that there are no or presence of pathologies.

When to take a test

The analysis is relevant for people of any age, because not everyone has been examined by a geneticist since early childhood. There are no contraindications for pregnant and lactating mothers. But first of all, research is required for newborns, for whom early diagnosis will help identify dangerous genetic diseases that affect life expectancy. An analysis in a hospital for the karyotype of spouses is often carried out as prescribed by a doctor, but not everyone knows what kind of examination this is. For couples wishing to have a child, an examination is indicated in the following cases:

After repeated unsuccessful attempts at conception.
Violation of the menstrual cycle.
If there have been miscarriages before, or dead children were born.
In children born earlier, a lag in mental or physical development was recorded.
Already at the stage of pregnancy, the fetus has developmental disorders.
If the future mother and father are close relatives.
If one of the parents has bad habits.
Living in a region with unfavorable environmental conditions or working in a hazardous industry.
Planning the first pregnancy after 35 years - the reason lies in the fact that with age, chromosomes can change.
If parents have genetic diseases, even if healthy children were born before.

Attention! Modern doctors advise all couples to be tested, since not every carrier has pathologies, and therefore many do not even suspect about them.

Problems, up to infertility, are revealed when a person decides to have a child.

How the study is done

The analysis is taken during the metaphase period, the duration of which is from two to ten minutes. It is at this point that it is easiest to see the chromosomes under a microscope. There are three ways to detect anomalies - molecular, cytogenetic and molecular targeted. The doctor should choose one or another method. Before the karyotype analysis is performed, it is necessary to prepare:

To cure colds, if a person is sick, then you can take an analysis no earlier than two weeks after recovery.
30 days before visiting the hospital, refuse to take antibiotics or reduce their consumption as directed by the doctor.
Do not drink alcohol for three days prior to testing.
On the day of the test, you need to have a hearty breakfast.

Venous blood is taken for testing. The material obtained from the patient is treated with a dye to reveal the chromosomes. Next, the doctor takes several pictures that allow you to determine the number of DNA molecules and pathological changes.

Important. The molecular method is necessary to detect small areas of structural chromosome anomalies less than 5 million nucleotides in size.

For more detailed diagnostics, an extended or targeted molecular method is used.

How to decrypt

For the representatives of the stronger sex, the normal karyotype results of the analysis are 46, XY, and for ladies - 46, XX. The number 46 indicates the number of chromosomes in the norm, and the X and Y at the end indicate the shape, structure and size of a healthy person - for men and women, these indicators differ. Based on the results of the tests, the doctor will make several marks on the form. Understanding medical terms will help decipher them:

Translocation - a rearrangement of a chromosome has occurred. If the patient has a balanced translocation, then it most likely will not manifest itself. If unbalanced, serious deviations are possible.
Mosaicism - Cells with genetic traits that are different from normal are found.
Trisomy - this pathology occurs most often, an extra chromosome is detected in a patient. The most common occurrence is the appearance of a copy of the 21st chromosome, leading to diseases such as Down syndrome.
Inversion - a section of the chromosome is rotated 180 degrees.
Monosomy - in the genotype, only one of the pairs of homologous chromosomes.
Deletion - a fragment of a chromosome is lost.

What to do if deviations are found

It should not be assumed that anomalies in the analysis of the karinotype always indicate that a married couple will have a sick child, or they will be completely childless. For example, parents with a balanced translocation can have a healthy baby who does not have chromosomal abnormalities. Even if the prices for karyotype analysis are high and start from three thousand rubles, it is undesirable to refuse it. Perhaps, based on the results, the doctor will advise you to undergo treatment and only then plan a pregnancy.

Attention! If a woman knows that she will have a child with pathologies, she needs to pay attention to a healthy lifestyle and follow the doctor's recommendations.

Genetic abnormalities can proceed in different ways. With trisomy of the thirteenth and eighteenth chromosomes, children die in the first year of life. People with Down syndrome are mentally retarded, but the mortality rate is much lower than with similar diseases. Sex chromosome anomalies, such as Shereshevsky-Turner syndrome, often lead to infertility, but a person with these disorders can live to old age. And with monosomy X, about 5% of women have the opportunity to give birth to a baby. It is important to consult a geneticist who will accurately diagnose. A genetic disease cannot be completely cured, but if treated regularly, the quality of life will improve.