Evolutionary rate of a gene affected by chromosomal position

Curr Biol. 1999 Sep 9;9(17):987-9. doi: 10.1016/s0960-9822(99)80430-8.


Genes evolve at different rates depending on the strength of selective pressure to maintain their function. Chromosomal position can also have an influence [1] [2]. The pseudoautosomal region (PAR) of mammalian sex chromosomes is a small region of sequence identity that is the site of an obligatory pairing and recombination event between the X and Y chromosomes during male meiosis [3] [4] [5] [6]. During female meiosis, X chromosomes can pair and recombine along their entire length. Recombination in the PAR is therefore approximately 10 times greater in male meiosis compared with female meiosis [4] [5] [6]. The gene Fxy (also known as MID1 [7]) spans the pseudoautosomal boundary (PAB) in the laboratory mouse (Mus musculus domesticus, C57BL/6) such that the 5' three exons of the gene are located on the X chromosome but the seven exons encoding the carboxy-terminal two-thirds of the protein are located within the PAR and are therefore present on both the X and Y chromosomes [8]. In humans [7] [9], the rat, and the wild mouse species Mus spretus, the gene is entirely X-unique. Here, we report that the rate of sequence divergence of the 3' end of the Fxy gene is much higher (estimated at 170-fold higher for synonymous sites) when pseudoautosomal (present on both the X and Y chromosomes) than when X-unique. Thus, chromosomal position can directly affect the rate of evolution of a gene. This finding also provides support for the suggestion that regions of the genome with a high recombination frequency, such as the PAR, may have an intrinsically elevated rate of sequence divergence.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Chromosome Mapping*
  • DNA, Complementary / genetics
  • Evolution, Molecular*
  • Female
  • Genes*
  • Humans
  • Male
  • Mice
  • Mice, Inbred C57BL / genetics*
  • Muridae / genetics*
  • Phylogeny
  • Proteins / genetics*
  • Rats / genetics*
  • Selection, Genetic
  • Sequence Homology, Nucleic Acid
  • Species Specificity
  • Ubiquitin-Protein Ligases
  • X Chromosome / genetics*
  • Y Chromosome / genetics*


  • DNA, Complementary
  • Proteins
  • Mid1 protein, mouse
  • Ubiquitin-Protein Ligases

Associated data

  • GENBANK/AF186460
  • GENBANK/AF186461
  • GENBANK/AF186462