Karyotype

Karyotype

Every organism consists of cells. Each cell contains a very specific amount of genetic information through a “carrier”, which we all now know that it is the DNA molecule. The DNA is organized in the nucleus of the cell, shaped as chromosomes. Every human being normally has 46 chromosomes in every somatic cell, which form 23 pairs of chromosomes. The two chromosomes of a pair are of the same size and morphology and contain the same genes- genes which define respectively the same characteristic of the organism. In all the chromosome pairs, one chromosome comes from our mother and the other from our father. In this way, both our parents inherit us the various “family” characteristics.

The number and the morphology of the chromosomes are strictly predefined in every normal somatic cell. Any deviation in the number or the morphology of the chromosomes can lead to various disorders and may be characterized as numerical or morphological anomalies. If the number of chromosomes is abnormal, then there are cases of aneuploidy. Aneuploidy includes cases of surplus or fewer chromosomes, compared to the normal number, which is 46 chromosomes for all the somatic cells for a normal human being. One of the most frequent and known aneuploidy syndrome is Down syndrome. People with Down syndrome have one extra chromosome 21 and that is why it is also called “Trisomy 21”. On the opposite, an aneuploidy case characterized by monosomy- lack of a chromosome- is Turner syndrome. Patients with Turner syndrome have only one X sex chromosome (XO), instead of a pair (XX).

The detection of structural and numerical chromosomal disorders can be done through the karyotype analysis of the person. As “karyotype” we define the diagrammatic depiction of the chromosomes of a somatic cell of a person, which are arranged by pairs and by size (from the biggest chromosome pair to the smallest). Examination of the karyotype can be done simply  with peripheral blood and analysis of the chromosomes of the white blood cells.

Karyotype analysis can detect aneuploidies and structural changes as well, thanks to the special processing of the chromosomes. Cases of structural abnormalities may include the absence of a chromosomal part, the duplication, or even the translocation of it to another chromosome. The analysis of the karyotype of a couple which encounters fertility problems is really important, as it may explain the subfertility or cases of recurrent miscarriages. The phenotype of a person may be absolutely normal, but on the same time there may exist a chromosomal abnormality. As a result, both normal and abnormal gametes (oocytes and spermatozoa) can be produced, which may be responsible for the infertility. Consequently, couples with a relevant history are recommended to do a karyotype analysis during the infertility investigation. The results of the analysis are available in just a couple of days and can be thoroughly assessed by the physician.