The concept of karyotype It has its origin in two words of the Greek language: karon, which can be translated as "nucleus" , and types (whose translation is "type" ). The notion, used in the field of biology , alludes to group of chromosome pairs that houses a cell .
The karyotype presents a specific amount of chromosomes , with a certain size and a certain shape, which is linked to the characteristics of a species . In the case of human being , the species usually presents 23 pairs of chromosomes : that is to say, 46 chromosomes in total in the nucleus of a cell. The organization of the human karyotype develops in 22 couples who are not sexual (autosomal) and a sexual pair .
In the karyotype of human being seven groups appear, each identified with a letter. These assemblies are formed according to the position and length of the centromere (a region of the chromosome that is in a characteristic place in each pair).
The human karyotype, therefore, is composed of Group A (the chromosomes of pairs 1, 2 and 3, which are the largest), the B Group (pairs 4 and 5, also large), the Group C (pairs 6 to 12 and the sexual pair), the Group D (pairs 13, 14 and 15), the Group E (pairs 16, 17 and 18), the Group F (pairs 19 and 20) and the Group G (pairs 21 and 22).
With respect to the single sexual pair of chromosomes of the human standard karyotype, mentioned in a previous paragraph, we can say that in the man , is formed by an X chromosome and another Y (XY pair ) while in the woman includes two X chromosomes (pair XX ). If this karyotype is constituted in another way, an abnormality in the development of the individual can be registered. The people with Down's Syndrome , for example, record the trisonomy of pair 21 : instead of two chromosomes in par 21, they have three.
In the clinical setting, this term and that of cariogram are often used interchangeably to refer to the latter, which is a analysis chromosomal cells in order to detect certain acquired and congenital diseases. In the case of people who wish to resort to assisted reproduction, for example, it is of great importance to carry out this test, especially if there is an ovarian failure, seminal alteration or abortions.
To carry out a cariogram it is necessary to make use of the so-called cells lipocytes, which can be obtained by blood collection. Another possibility, if the patient is a woman pregnant , is to take it from the amniotic fluid.
The karyotype allows us to appreciate the diversity of chromosomes, since all are distinguished from others by their size, shape and by the arrangement of the bands that are noticed throughout their body. Thanks to the cariogram it is possible to detect several alterations , which can be numerical or structural. One of the most common examples is in Down syndrome, whose alteration is numerical and is detailed above.
Another known numerical alteration is the Klinefelter syndrome , which occurs in men and causes problems of reproduction ; precisely, a failure in the testicles appears that usually triggers infertility disorders. In this case, two X chromosomes and one Y are noticed.
He turner syndrome On the other hand, it appears in women who have only one X chromosome. The lack of the other means that sexual characteristics cannot develop completely, which is why the body is unable to reproduce sexually.
In structural alterations some chromosomal regions may be absent or duplicated , and this can lead to various types of consequences, depending on the genes That are compromised.