Is this a biological paradox? (1 Viewer)

[Leadmen4y]

A point mutation is defined as a mutation in a single nucleotide. The HSC defines it this way as well. Cystic fibrosis is a point mutation, yet it effects 3 nucleotides. So how is it a point mutation?

maybe "multiple" point mutations? You can't say a disease is a mutation, it's the effect of a cause (in this case mutation). you should say "cystic fibrosis occurs as a result of...". also I just remembered, a point mutation affecting multiple nucleotides is perfectly normal, if it's a frameshift rather than substitution.

 

[jimmysmith560]

Would the below information help?

Cystic fibrosis (CF) is caused by a single point mutation in the cystic fibrosis membrane conductance regulator (CFTR) protein. CFTR is a chloride channel located in the apical membrane of epithelial cells and plays a fundamental role in transepithelial salt and water movement.

 

[Eagle Mum]

It’s not a paradox - just a bit more complex. There are >2000 identified variants in the CFTR gene and >300 of these cause cystic fibrosis.

The most common mutation (deltaF508, HGVS name c.1521_1523delCTT), which I think you are referring to, is a deletion of three nucleotides, so one crucial amino acid is missing from the final protein.

There are also many single point substitution mutations which cause cystic fibrosis (the more common ones being c.254G>A, c.1364C>A), as well as several single point deletion mutations (eg. c.948delT).

There is a website which has catalogued the CFTR mutations which cause cystic fibrosis: https://cftr2.org/

You should also know that there are many other gene/disease combinations which can be similarly caused by not just one type of mutation but by a variety of other types of mutations (noting that often only one mutation on each allele will result in an autosomal recessive disease condition).

 

[Eagle Mum]

maybe "multiple" point mutations? You can't say a disease is a mutation, it's the effect of a cause (in this case mutation). you should say "cystic fibrosis occurs as a result of...". also I just remembered, a point mutation affecting multiple nucleotides is perfectly normal, if it's a frameshift rather than substitution.

It depends on whether the substitution of nucleotide(s) causes an amino acid substitution. If so, then it also depends on how similar/dissimilar the amino acids are (within the same dibasic, neutral, acidic group?) and whether a disulfide bridge is destroyed or created. Even if there is no amino acid change, a splice site may be created or disappears.