Chromosome analysis is a test that evaluates the number and structure of a person's chromosomes, in order to detect birth defects, and certain genetic abnormalities present in the blood of parents or the fetus.
Chromosomes are threadlike structures, found within the nucleus of each cell. They contain the body's genetic blueprint. Each chromosome holds thousands of genes at specific locations. These genes are responsible for the inherited physical characteristics of an individual. They have a profound impact on growth, development, and function of a human body.
Every individual normally has 23 pairs of chromosomes in each cell (23 pairs = 46 chromosomes). One of these pairs carries chromosomes - X and Y; chromosomes which determines gender of a human being. For a male, the combination is of an XY pair and for a female, it’s an XX pair. The remaining 22 pairs of chromosomes are called autosomes.
Chromosomal abnormalities include both numerical and structural changes. For numerical changes, anything other than a complete set of 46 chromosomes, represents a change in the amount of genetic material present causing and can cause health and development problems. For structural changes, the significance of the problem and their severity depends on the chromosome that is altered. The type and degree of the problem may vary from person to person, even when with same chromosomal abnormality.
Abnormalities in chromosomes help the healthcare providers diagnose several medical conditions. In some cases, the chromosomes can help predict a medical problem, even before showing symptoms. Chromosome studies done on a developing baby, especially inside a mother's womb can help identify problems that the baby may be born with or develop later in life.
Why Do You Need This Test?
You may need this test for a variety of reasons, such as helping diagnose a disease, identifying any abnormal chromosomal defect that may be passed on from parent to child, and more. Here are the most common reasons to have this test;
To find out if you are at a risk of developing a disease that you may have inherited
To find out if you are carrying genes that may pass a disease to your children
To find out if your unborn child has any chromosomal problem
To find out why you are having trouble getting pregnant
To find out why you are having miscarriages or losing a baby before birth
To find out if any chromosomal abnormality associated disorder signs are present
LifeCell Diagnostic Cytogenetic Test Options
It requires experience and expertise to perform the test properly and to interpret the results. While theoretically, almost any cell could be used for testing, in practice, it is usually performed on a Chorionic Villus Sample or Amniotic Fluid to evaluate a fetus, and on Lymphocytes (a white blood cell), from a blood sample, for all other ages.
How is the test performed?
- Taking a sample of a person's cells and culturing them in nutrient-enriched media to promote cell division in-vitro. This is done in order to select a specific time during the cells' growth phase when the chromosomes are easiest to distinguish.
- Isolating the chromosomes from the nucleus of the cells, placing them on a slide, and treating them with a special stain.
- Taking microphotographs of the chromosomes.
- In jigsaw puzzle fashion, rearranging the pictures of the chromosomes to match up pairs and arrange them by size and structure, from numbers 1 to 22, followed by the sex chromosomes as the 23rd pair.
- The pictures also allow the chromosomes to be vertically oriented. Each chromosome looks like a striped straw. It has two arms that differ in length (a short arm (p) and a long arm (q)), a pinched-in area between the arms called a centromere, and a series of light and dark horizontal bands. The length of the arms and the location of the bands help determine top from bottom.
- Once the chromosome photo arrangement is completed, a laboratory specialist evaluates the chromosome pairs and identifies any abnormalities that may be present.
Why is this Test Important?
If the results show an odd number of chromosomes, differently placed chromosomes, or deformed chromosomes, it can be an indication of a genetic condition. Genetic conditions are not always the same, but the two most common examples are Down Syndrome and Turner Syndrome. With the help of Karyotyping, your specialist can identify various other genetic conditions as well. For instance, for a woman who has suffered from premature ovarian failure, Karyotyping can determine if it is because of a chromosomal defect.
It is possible to karyotype test the babies prior to their birth to see if they have any genetic anomalies that can lead to severe birth defects, such as Klinefelter Syndrome. In this syndrome, the boy is born with an additional X chromosome.
Are There Any Risks Associated with This Test?
Although very rare, complications can be caused because of the testing methods. There is a minute risk of contracting an infection or going through excessive bleeding after your blood test or after having the bone marrow biopsy. Amniocentesis can cause a very slight risk of a miscarriage.