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No clear correlation exists between the size and localization of the deletions and the testicular phenotype.
b, The seven intervals of the Vergnaud map of the Y chromosome (8), where intervals 1–4 span the short arm and the centromere, intervals 5 and 6 span the euchromatic region, and interval 7 spans the heterochromatic region. On the Representation of the cytological bands of the Y chromosome.
In the initial stages, spermatogonia divide via mitoses, giving rise to primary spermatocytes, which in turn undergo the first meiotic division leading to secondary spermatocytes.
Through the second meiosis these cells produce haploid cells (round spermatids), which elongate during the spermiogenesis process (elongated spermatids) and finally differentiate into mature spermatozoa, by condensation of the chromatin, substitution of histones with protamines, and formation of the acrosome and the other sperm components.
The explosive growth of assisted reproduction techniques and, in particular, of intracytoplasmic sperm injection (ICSI) (7) has contributed to the development of such research.
The study of Y chromosome microdeletions is particularly important because of the potential for transmission of genetic abnormalities to the offspring, as these techniques bypass the physiological mechanisms related to fertilization.