Ychromosomale

YChromosomale, commonly referred to as the Y chromosome, is one of the two sex chromosomes in humans and many other mammals. It determines male development in combination with the X chromosome and is transmitted from father to son, providing a direct record of paternal inheritance. The Y chromosome is comparatively small and gene-dense in important regions, with most of its sequence falling into noncoding and repetitive elements.

It contains the sex-determining region Y (SRY), which initiates male gonadal development by triggering testis formation. In addition to SRY, the chromosome harbors genes involved in spermatogenesis and sperm function, including members of the AZF region. The majority of the Y does not recombine with the X chromosome and forms the non-recombining region of the Y (NRY or MSY); small portions at the ends—the pseudoautosomal regions PAR1 and PAR2—recombine with the X during meiosis.

Inheritance of the Y chromosome is strictly paternal; it changes only through mutation. As a result, Y-chromosome variation is used to define Y-DNA haplogroups and to reconstruct patrilineal ancestry. This inheritance pattern also makes Y-chromosome analysis useful in forensics and population genetics, especially through Y-STR markers.

Evolutionarily, the Y chromosome is believed to have originated from an ancestral autosome and has undergone gene loss and structural rearrangements over hundreds of millions of years. Today it retains a set of essential male-specific genes, but many former genes have degraded or been lost. Repetitive sequences and palindromic regions in the MSY may facilitate intrachromosomal rearrangements and deletions, including clinically relevant Y-chromosome microdeletions that can cause infertility.