I'm prepping an activity for my biology students on cystic fibrosis. There are about 2000 different mutations of the CFTR gene that cause CF. Since the final phenotype is pretty much the same, can I still claim that all these mutations represent different alleles?

I like to point out that genes tend to have more than two alleles - it's something that students really struggle with. But if every allele needs to have a different phenotype based on the standard definition, then this isn't ideal.

Thanks for the help.

  • 2
    $\begingroup$ I agree with the answer given by @Bez. The problem arises because the term "allele" was coined in an era when the only way to observe (or infer) the existence of different forms of a gene was through the associated change in phenotype (i.e. genes were not observable directly). Now that we can document single base changes via sequencing, the link to observable phenotype has been completely severed, but the idea of alleles as alternative forms of a single gene is still useful. $\endgroup$
    – Alan Boyd
    Jun 14, 2014 at 8:26

1 Answer 1


Yes, allele is an alternative form of the same gene which can be produced through any variations/mutations of a gene, such as deletion, segmental duplications, inversions, insertions through transposons, even a SNP or point mutation (http://en.wikipedia.org/wiki/Allele) and as correctly stated many alleles do not produce any observable/discernable phenotypic variation. A gene can have many alleles in a given population, but do not confuse allele with gene homologues (which I suspect what you were alluding to above in the second paragraph), which are similar versions of a gene such as RIN1, RIN2 and RIN3 (http://homepage.usask.ca/~ctl271/857/def_homolog.shtml).


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .