Selection against deleterious LINE-1-containing loci in the human lineage

Stéphane Boissinot, Ali Entezam, Anthony V. Furano

Research output: Contribution to journalArticlepeer-review


We compared sex chromosomal and autosomal regions of similar GC contents and found that the human Y chromosome contains nine times as many full-length (FL) ancestral LINE-1 (L1) elements per megabase as do autosomes and that the X chromosome contains three times as many. In addition, both sex chromosomes contain a ca. twofold excess of elements that are >500 bp but not long enough to be capable of autonomous replication. In contrast, the autosomes are not deficient in short (<500 bp) L1 elements or SINE elements relative to the sex chromosomes. Since neither the Y nor the X chromosome, when present in males, can be cleared of deleterious genetic loci by recombination, we conclude that most FL L1s were deleterious and thus subject to purifying selection. Comparison between nonrecombining and recombining regions of autosome 21 supported this conclusion. We were able to identify a subset of loci in the human DNA database that once contained active L1 elements, and we found by using the polymerase chain reaction that 72% of them no longer contain L1 elements in a representative of each of eight different ethnic groups. Genetic damage produced by both L1 retrotransposition and ectopic (nonallelic) recombination between L1 elements could provide the basis for their negative selection.

Original languageEnglish (US)
Pages (from-to)926-935
Number of pages10
JournalMolecular Biology and Evolution
Issue number6
StatePublished - 2001


  • Evolution
  • Human
  • L1/LINE-1
  • Retrotransposon
  • Sex chromosome

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Molecular Biology
  • Genetics


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