7/28/2019 Edexcel Unit 1 Notes Cystic Fibrosis

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Adam Clarke www.brain-freeze.co.uk

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2.4 In-depth study of a genetic diseases - Cystic fibrosis

Cystic fibrosis is an inherited disorder that mainly affects respiratory, digestive and

reproductive systems. It is caused by a recessive allele so a person will only have

the disorder if theyre homozygous for the allele they must inherit one recessive

allele from each parent. If a person is heterozygous they wonthave CF but theyll be

a carrier.

Cystic fibrosis causes the production of thick sticky mucus.

1) Caused by mutation in the gene that codes for CFTR protein

( Cystic Fibrosis Transmembrane Conductance Regulator)

2) CFTR is a carrier protein which transports chloride ions out of cells and into mucus

causes water to move into the water by osmosis which makes it watery

3) Mutant CFTR is much less efficient at transporting chloride ions out of the cell, so

less water moves out by osmosis makes the mucus of people with CF abnormallythick and sticky.

4) The thick and sticky mucus causes problems in the respiratory, digestive and

reproductive system.

Respiratory system

Mucus prevents lung infections by trapping microorganisms. The mucus including

microorganisms is then transported towards the throat by cilia (hair like structures

that beat to move mucus). In those suffering from CF the mucus is abnormally thick

and sticky, which causes some problems.

1) The cilia are unable to move the mucus towards the throat because it becomes

thick and sticky

2) The mucus builds up in the airways

3) Some airways can become completely blocked by the mucus- gas exchange cant

take place in the area below the blockage

4) This means that the surface area available for gas exchange is reduced, causing

breathing difficulties.

The digestive system1) Tube connects the pancreas to small intestine blocked with mucus- preventing

digestive enzymes produced by the pancreas from reaching the small intestine.

Difficult to digest food - fewer nutrients are absorbed.

2) The mucus can cause cysts (growths) to form in pancreas these inhibit the

production of enzymes which also reduces the ability to digest food and absorb

nutrients.

3) The mucus lining the small intestine is abnormally thick inhibits absorption of

nutrients.

7/28/2019 Edexcel Unit 1 Notes Cystic Fibrosis

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Adam Clarke www.brain-freeze.co.uk

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Reproductive system

Mucus is secreted here to prevent infections / transport sex cells.

1) Men tubes connecting testicles to penis are absent in some / can be blocked by

mucus sperm cant reach penis

2) Women thickened cervical mucus prevent sperm reaching the egg travel

through mucus to reach the egg thick mucus reduces the motility of sperm

reducing chances of it making the journey to the egg.

Treating cystic fibrosis

Physiotherapy

Makes it easier to breathe take in enough oxygen reduce risk of lung infections

Devices can change the pressure in the airways and help people to clear their mucus

without using more vigorous physiotherapy are being introduced flutter, positive

expiratory pressure valve and the ThAIRapy bronchial drainage system.

Diet and enzymesMucus blocks pancreatic duct /lining of the gut digesting absorbing food is

difficult.

Take enzymes with meal replace missing pancreatic enzymes so more food can

be digested.

More foodmake up for what isnt digested

High-energy /fat/carbohydrate foods twice as much protein

Drug therapies

Antibiotics destroy bacteria for lung infections aerosols (inhalers) used to

breathe them deep into the lungs.Vaccines childhood vaccines yearly flu vaccine pneumonia

Mucolytics these are drugs to make mucus runny / easier to move

Asthma drugs e.g. salbutamol and steroids used to open airways / reduce

inflammation in lungs

DNAase enzymes make mucus thinner and easier to cough up

Insulin problems with pancreas lead to diabetes insulin required control

blood concentration

Transplant surgery

Damage so severe e.g. to heart or lungs transplant of organ requiredNew organs wont be affected by CF rest of body will still have other problems

After a transplant the person has to take immunosuppressant drugs prevent body

reacting against the new tissue and rejecting it. This suppresses the immune system

making it harder to fight infections.

Infertility treatments

IVF for men sperm fertilise eggs in vitro embryo return to uterus to develop

normally.