 Cystic fibrosis Cystic fibrosis is a genetic disease that varies in incidence across the globe. The majority of people with cystic fibrosis are of Caucasian descent and so therefore the disease is most prevalent in North America, Europe and Australasia. In the European Union, 1 in every 2 to 3,000 newborns are affected by cystic fibrosis. It is caused by a defective gene on one of the chromosomes which has been inherited from the parents. The severity varies greatly from person to person and largely depends on how much the lungs are affected. Deterioration in conditions is inevitable and eventually leads to death. Whilst today is currently no cure or effective treatment, treatments can slow some of the changes that occur in the lungs. Progress is being made in treatments. Only 30 years ago, life expectancy was pre-adulthood. Today, the median age of sufferers is 33 years old with many patients living into their 50s and 60s. Gene therapy holds great promise for treating cystic fibrosis. The defective gene causes the body to produce lots of thick, sticky mucus in the lungs which has to be removed by a massage. Sufferers are prone to chest infections. It also causes excess mucus in the pancreas. Symptoms tend to start early in childhood however they may not be obvious until adulthood. The genetics of cystic fibrosis is actually quite simple. It is caused by a mutation on a specific gene. This is a recessive gene and is carried by about 1 in every 25 people in the UK. Because it is a recessive gene, it means that you can be a carrier but not suffer from the condition and also your children will not necessarily inherit the mutation. Cystic fibrosis carriers have one normal gene and one mutated gene. If both parents are carriers of the cystic fibrosis gene then it can be passed on to their child. The child inherits one chromosome from each parent. If the child gets both copies of the chromosome containing the cystic fibrosis gene then they have two copies of the mutation and so will be born with cystic fibrosis. However if they inherit one of the chromosomes carrying cystic fibrosis and one normal chromosome they will be a carrier of cystic fibrosis but will not actually have it themselves. If one parent is not a carrier then there is no risk of having a child with cystic fibrosis because it is a recessive gene and so the dominant healthy gene overrides it. There is a test available to see if you are a carrier. So from this video you should know that cystic fibrosis is caused by a recessive allel and that it is a deteriorating disease that causes surplus mucus in the body. Treatments are improving and gene therapy is looking hopeful. And if the child inherits both of the normal chromosomes then they will not have cystic fibrosis and will not be a carrier either. So the possible combinations of two cystic fibrosis carrying parents are normal from mom and mutation from dad gives a carrier child. Normal from dad and mutation from mom gives a carrier child. Normal from mom and normal from dad gives a fully cystic fibrosis free child. Mutation from mom and mutation from dad gives a child with cystic fibrosis. So if both parents are carriers then there is a 25% chance that the child will have cystic fibrosis, 25% they will not and 50% chance the child will be a carrier.