Cystic fibrosis

Welcome back to my blog ‘The diverse nature of genetic disorders’, this week we are looking into the genetics behind Cystic fibrosis.

(Credit: LiveScience)

Cystic fibrosis (CF) is an inherited condition that induces a build-up of sticky mucous in the lungs and gastrointestinal tract. Patients will present with recurrent chest infections, respiratory issues, diarrhoea, difficulty gaining weight, and bowel obstruction. The majority of cases are diagnosed at birth, with symptoms getting progressively worse as the individual ages due to increased damage. 

(Credit: Verywell Health)

This condition is caused by a mutation to a gene on chromosome 7 that encodes for the protein cystic fibrosis transmembrane conductance regulator (CFTR). The faulty gene affects water and salt movement in and out of the cells. There is reduced secretion of chloride and increased resorption of sodium in cells. As more sodium enters the cell, more water also enters; this causes a build-up of thick sticky mucous that the cilia cannot sweep away.  

(Credit: Respiratory care)

Cystic fibrosis is inherited in an autosomal recessive manner. An individual must possess two mutated CFTR genes, as shown in the punnet square below. If both parents are carriers, the offspring has a 25% chance of being unaffected, 25% having two mutated genes (Cystic fibrosis), and 50% having one mutated gene (carrier). 
(Credit: Biorender)

There are over 2,000 identified mutations to the CFTR gene, which can be categorised into six classes, explained further in the table below. The CFTR channel protein functionality will determine what class the mutation is. The most common mutation is the class II mutation ΔF508, which occurs in 70% of Cystic fibrosis cases.
(Credit: Biorender)

Although Cystic fibrosis is a life-threatening condition, therapies have advanced so that more than half of CF patients will live past the age of 40. With increased research into mutations to the CFTR gene, patients' quality of life will improve along with their life expectancy. 

Thank you for reading to the end. In the next blog, we will uncover the genetics of Turner’s syndrome, so look out for the next post!

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