Cystic fibrosis allele frequency, sex ratio anomalies and fertility: a new theory for the dissemination of mutant alleles

Hum Genet. 1991 Oct;87(6):671-6. doi: 10.1007/BF00201723.


The observation that mothers of cystic fibrosis patients come from sibships that are larger than those of the fathers is explained by a decrease in sex ratio with increasing size of parental sibships. This feature also provides the basis for a new theory for the dissemination of the major mutant allele, deduced to have arisen 2,700-5,000 years ago, in accordance with an overall heterozygote advantage of around 3%. In heterozygous women with heterozygous partners, sex-related selection probably occurs after fertilization.

MeSH terms

  • Alleles
  • Cystic Fibrosis / genetics*
  • Female
  • Fertility
  • Gene Frequency
  • Humans
  • Male
  • Mutation*
  • Sex Ratio