Why Do You Think Another Mistake Doesn't Just "Correct" The Mutation In An Abnormal CF Gene?


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Deborah Mann answered
  • Cystic Fibrosis.
This is a genetic condition that causes, amongst other things, severe build up of mucus inside the lungs. This has to be coughed up regularly, and the life span of a cystic fibrosis sufferer was severely limited by the condition before the development of adequate antibiotics.

Cystic fibrosis sufferers cannot digest certain fats or absorb them and it is caused by inheriting two copies of defective gene, which means that the mucous glands in the digestive, respiratory, reproductive and sweat glands do not function properly.

  • Corrective Mutation
Simply put, the amount of mutations that could happen in the combination of genes from the DNA will not balance things out, but complicate them hugely. It is worth noting that just like CF, many mutations can be lethal to the mutant, killing it.

Mutations occur through the following methods:

  • Deletion
A sequence of DNA nucleotides are removed in the copying/separation process. The missing genes do not affect the overall growth of the organism, causing missing features.

  • Insertion
Nucleotides cross over and insert themselves into the sequence of the DNA.  This leads to the formation of mutations.

  • Chromosomal Interchange.

Here, parts of the DNA become transposed or just moved around. Again, this can become a mutation. Whole parts of the DNA become swapped or moved in this process.

  • Point Mutation.

DNA nucleotides are moved around inside the DNA strand.

Due to the statistical vagaries of the whole process, the chances of an insertion mutation happening to delete the existing CF mutation would be almost infinitesimal and there would be a greater chance of winning the lottery or being struck by lightning.

The whole process of cellular division is too complex to randomly hope that a mutation would simplify the situation. In reality, it is more likely to make things worse.

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