Increased Recombination Rates

Human telomeres have increased genetic recombination rates compared to other regions in the genome. Genetic recombination rates have been shown to increase in the telomeric regions for both sexes in human, but dramatically so in males. Although female recombination rates are generally higher than males for most regions of the genome, this pattern is reversed at telomeres where male recombination is significantly higher than female (Blouin et al., 1995; Donis-Keller et al., 1987; Rouyer et al., 1990). 

This high rate of recombination at telomeres could play a role in unequal exchange and gene dosage imbalance, as has been observed in both pseudoautosomal regions (PAR) of the X and Y chromosomes. Unequal recombination in the PAR1 region (Xp;Yp) accounts for 80% of XX males (1/20,000 male births), due to translocation of the SRY gene to Xp (Rouyer et al., 1987; Weil et al., 1994).  The reciprocal unequal product is observed in some XY females who are deleted for SRY. Similar unequal exchange events affecting the PAR2 region (Xq;Yq) have been observed which lead to a severe mental retardation syndrome in males with Yq- karyotypes (Lahn et al., 1994).