 To show examples of diseases inherited through dominant and recessive alleles.  To be able to correctly predict the outcome of various combinations of parent genotypes.

 Mental degenerative disease;  Develop uncontrolled movements  Develop form of dementia  Lose ability to swallow  Often associated psychological problems  Onset usually in middle age  Can be early < 20 or later  Death occurs within 20 years of onset  Usually faster in younger sufferers

 It is autosomal dominant  Need only one allele from one parent  If you have the gene you will inherit the disease;  Can get worse from generation to generation  Especially if carrier is father  Some people have only very mild version with no obvious signs  Thus a person with no family history can develop the disease

 Mutant gene affects the production of a protein called Huntingtin;  Role of Huntingtin in body not well understood; mostly present in brain and testes  Interacts with proteins involved in transcription, cell transport and cell signaling  May be important in gene transcription and the development of nerve cells especially in embryos  Mutant Huntingtin damages the nerve cells in the brain gradually causing the development of symptoms

 Huntingtin gene has multiple repeats of the trinucleotide CAG  Mutant gene has extra repeat segments  The resulting disease status, depends on the number of CAG repeats  <28 Normal Unaffected  28–35 Intermediate Unaffected  36–40 Reduced Penetrance +/- Affected >40 Full Penetrance Affected  >60 Onset before age of 20

 An unmutated gene has less than 28 – most people  Full penetrance means you will have it and have a 50% change of passing it to your child  Intermediate will either be weak and very late onset or not at all  Often not noticed

 Gene is unstable  Especially in spermatogenesis it can get longer  How is this relevant to which parent has it?  How might this affect families with intermediate genes?

 5 – 10 cases per people world wide  Much commoner in people of western European origin – mixed race 7 per  Very rare in Asians and Africans 0.1 per  Clusters in certain isolated populations: Lake Maracaibo Venezuela, 700 per

 No cure  Treatment can alleviate symptoms  Some medications to reduce involuntary actions  Some mediations to tackle psychological issues.

 Also known as mucoviscidosis (sticky mucus)  Developmental disease  Lungs do not develop properly  Digestive system does not absorb food  Pancreas stops functioning  Observed in infancy  Untreated leads to very early death  Treated increases survival but likely to reduce growth  Some people seem very healthy  Others seriously compromised

 Many respiratory infections  Poor growth due to malnutrition  Diabetes due to damage to pancreas  Intestinal blockage in newborns  Sterility due to blockage of sperm duct (sperms fine)  Cirrhosis of the liver

 This is a recessive disease  This means you must have both alleles to have the disease;  If you have one allele you are a carrier and do not show the disease;  Both parents must be carriers for a child to have a disease  Chance of having disease is 1 in 4

 CF is caused by a mutation in the gene for the protein cystic fibrosis transmembrane conductance regulator (CFTR);  This protein regulates the components of digestive juices, sweat and mucus;  Only one healthy gene is needed for this to function

 There are over 1500 possible mutations to the CFTR gene that can lead to CF  Over 60% of cases worldwide are due to one specific mutation;  Screening usually tests for up to 32 different mutations, but this does mean that some cases can be missed by screening.

 Commonest in western European Caucasians (1 in 25 are carriers)  Highest prevalence in Ireland  Non European populations much rarer and usually a different mutation (1 in 46 Hispanics in US, 1 in 65 African Americans)  In 1959 median age of survival was 6 months  The median survival age in Canada has increased from 24 in 1982 to 47.7 in 2007

 Possible cure through introduction of gene to airways – early stages  Treatment of lung diseases through antibiotics  Preventative use of antibiotics  Physiotherapy to help clear lungs of fluid  Replacement of digestive enzymes (pills)  Insulin  Healthy diet and exercise  May need lung, liver and pancreas transplants  Assisted reproduction

 At risk adults may get genetic testing.  Expensive so usually only one parent done at first (many mutations screened for)  Pre-implantation genetic diagnosis  Testing of foetus in utero by amniocentesis or chorionic villus sampling of placenta  Screening of new born: test sweat  Parents may notice baby tastes salty  Worst option wait till respiratory complications and poor growth show;  Best prognosis with earliest diagnosis

Carries a risk of about 1 in 200 of initiating an abortion

 What ethical issues surround the following decisions  1. To start a family  2. To test foetuses  3. To decide against having a child  4. Gene testing and medical records

 Research another genetically inherited disease  It must be dependent on one gene – rules out diabetes, heart disease and breast cancer which only have genetic links  Write a two page report on the disease  Follow rubric for guidance

 1. Description of disease 3 points  2. Explanation of inheritance 5 points  3. Treatments, cures and preventions 4 points  4. Spelling and grammar 3 points ( 20 = 1 point)  Presentation (5 points): intelligently chosen visual material (2) Captions(1), Subheadings, (1) references (1)