Pseudoautosomal region

Pseudoautosomal region (PAR) is a small region of chromosomes that have the same sequence of nucleotides in both the male and female. This region is present on both the sex chromosomes X and Y. The term "pseudoautosomal" refers to the fact that this region undergoes recombination during meiosis, a characteristic of autosomes but not of typical sex chromosomes.

Characteristics

The pseudoautosomal region is unique because it is the only region where the X and Y chromosomes pair and exchange genetic material during meiosis. This process, known as crossing over, is essential for the proper segregation of chromosomes during the formation of gametes.

There are two pseudoautosomal regions in humans, PAR1 and PAR2. PAR1 is located at the end of the short arm of the X and Y chromosomes (Xp22 and Yp11), while PAR2 is found at the ends of the long arms (Xq28 and Yq12).

Genes in the Pseudoautosomal Region

Several genes have been identified in the pseudoautosomal region. These genes are expressed in both males and females, as they are present on both the X and Y chromosomes. Some of the genes identified in this region include the SHOX gene, which is involved in skeletal development, and the IL9R gene, which encodes the interleukin-9 receptor.

Clinical Significance

Mutations in the genes located in the pseudoautosomal region can lead to various genetic disorders. For example, mutations in the SHOX gene can cause Leri-Weill dyschondrosteosis, a disorder characterized by short stature and skeletal abnormalities.

See Also

• Sex chromosomes
• Autosomes
• Genetic recombination
• Meiosis