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Meiosis

What is meiosis?
Meiosis is the process by which the mother cells of the spermatozoa (or spermatogonium) reduce their chromosome pool by half; in other words they go from 46 to 23 chromosomes, which are the ones that form each sperm cell.

How is alteration of meiosis studied?
It is normally carried out from analysis of the testicular tissue by a testicular biopsy. From this tissue, the precursor cells of the sperm cells in the different phases of meiosis are obtained. This allows assessment of whether the chromosomal distribution is correct.

Which males may have alterations in meiosis?
It is advisable to request this technique in the following situations:

  • Men who have had 3 unsuccessful IVF cycles.
  • Men from couples with recurrent miscarriage when the other tests from the infertility study are normal.
  • When no spermatozoids are found in a semen analysis (azoospermia), or in patients with any type of seminal alteration as for example a low sperm count (oligozoospermia).

What are the repercussions of meiotic abnormalities?
Sperm with a higher or lower number of chromosomes than normal may be the cause of embryos with anomalies that in turn may result in a lack of pregnancy, a first trimester spontaneous abortion, or the birth of a child carrying an alteration.

Is there any treatment for meiotic abnormalities?
These alterations cannot be treated and there are a poor prognosis of fertility for those who have them. This does not mean that these men cannot produce a minimum percentage of chromosomally normal sperm cells, but there is no technique for separating the chromosomally balanced sperm cells from those that are not for subsequent use in reproduction treatments. However, the fertility prognosis may be improved by analyzing the embryos using preimplantation genetic diagnosis (PGD) techniques.

Meiosis in Images:

1.Prophase I normal.
Lepto-zygotene stage.
2.Prophase I normal.
Paquitene stage.
3.Prophase I with
pairing abnormalities.
Paquitene stage.
4.Metaphase I normal.
5.Metaphase I with generalized
Desynapsis of bivalents.
6.Metaphase II normal.

 

 
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