In article <5oboht$8t7 at gap.cco.caltech.edu>, mathog at seqaxp.bio.caltech.edu
> I recall hearing somewhere or other that heterozygotes for cystic fibrosis
> have increased fertiility, but do not recall the reference, or even if it
> was in a journal or just the lay press.
Don't think so. One type of CF mutation is now known to cause congenital
absence of the vas deferens and there's also some evidence for low-level
impaired epididymal function leading to lowered fertility.
1. Dumur V, Gervais R, Rigot JM, Delomel-Vinner E, Decaestecker B,
Lafitte JJ, et al. Congenital bilateral absence of the vas deferens
(CBAVD) and Cystic Fibrosis transmembrane regulator (CFTR) - correlation
between genotype and phenotype. Human Genetics 1996;97(1):7-10.
2. Vanderven K, Messer L, Vanderven H, Jeyendran RS, Ober C. Cystic
fibrosis mutation screening in healthy men with reduced sperm quality.
Human Reproduction 1996;11(3):513-517.
There was a suggestion some time back that CF carrier status gave
protection against some forms of intestinal disorders but the geographical
distribution of CF does not fit this hypothesis.