Chromosome Y


The mapping and sequencing of the human Y chromosome have permitted detailed study of its evolution and an assessment of its genetic functions. The human Y chromosome is an acrocentric chromosome containing 1.6% of the genome and exhibiting a very low gene density. It is unique insofar as it is the only chromosome that does not recombine along the majority of its length and it is only present in males.

Keywords: Y chromosome, non‐recombination, genetic degeneration, male

Figure 1.

Model of the human Y chromosome showing the key features of its organization: two strictly X–Y homologous pseudoautosomal pairing regions (PAR1 and PAR2), where there is genetic exchange between the X and Y; and the nonpairing, nonrecombining region of the Y (NRY) composed of the Yq heterochromatin and the euchromatic sequences.

Figure 2.

Summary of the major regions of the Y chromosome that share homology with the X chromosome. The species in which the loci first became X–Y homologus is indicated by the shading. The evolutionary relationship between the phyla represented gives an indication of their age on the Y chromosome. The figure also shows the point in time when two Y/autosomal sequences appeared on the Y chromosome (CDY and DAZ). The representation of when sequences appeared on the sex chromosomes is based on Southern blot and fluorescence in situ hybridization of XY loci. Some of the sequences located in the NRY on the human Y chromosome may be found in the PAR of other species; for example, STS is PAR in the mouse. The arrows highlight regions unique to the human Y chromosome.

Figure 3.

Summary of the organization of the AZFa male infertility interval showing the arrangement of genes, pseudogenes and (HERV15) direct repeats. The figure also shows the location of breakpoints for two patients where it has been reported that an unequal recombination event has occurred between HERV15 repeats. BAC: bacterial artificial chromosome.

Figure 4.

Organization of inverted and direct repeats across the AZFc male infertility interval, together with the distribution of genes mapped to this part of the Y chromosome.



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Further Reading

Affara NA and Mitchell M (2000) The role of the human and mouse Y chromosome genes in male infertility. Journal of Endocrinological Investigation 23: 630–645.

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Web Links‐bin/nomenclature/ Genew: Human Gene Nomenclature Database Search Engine HUGO approved gene nomenclature and links to further information

NCBI (National Center for Biotechnology Information). This site provides a comprehensive series of links to the most recent publically available genome data

NCBI LocusLink A single query interface to curated sequences and descriptive information about genetic loci. Contains information on official nomenclature, aliases, sequence accessions, phenotypes, MIM numbers, homology, map locations, related websites among others

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Affara, Nabeel A, and Sargent, Carole A(Jan 2006) Chromosome Y. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1038/npg.els.0005925]