Lecture 8

Question 1

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Single Gene disorders

Answer 1

• Caused by point mutations in single genes
• High morbidity in children
• Affect 1-5% of population
• Most currently incurabel
• Cost NHS over £2 billion

Question 2

An autosomal recessive pedigree

Answer 2

• Males and females affected
• Disease absent in most generations
• Incest increases frequency
• Carriers have 25% of affected children

Question 2

Cystic fibrosis

Answer 2

• Autosomal recessive
• 1 in 25 carriers
• 1 in 2500 births
• Mucus in lungs , pancreas and other organs
• Chronic Bronchitus
• Recurrent bacteril infections

Question 3

What causes CF?

Answer 3

• CF codes for a chloride channel which regulates mucus
• Deletion of a 3 bp leads to the los f a Phe (F) residue at pattern 508
• Protein is now abnormally shaped and is more quickly degraded

Question 4

CF treatment

Answer 4

Treated by anti-biotics and daily massages to clear mucus

Question 5

Sickle cell anemia

Answer 5

• Autosomal recessive
• Anemia, joint pain, swollen spleen, severe infections
• Mutations in B haemoglobin chain leading to incorrect folding
• Treated by blood transfers
• Malaria resistent, heterozygote advantage

Question 6

Autosomal dominant pedigree

Answer 6

• Males and females affected
• Affected children have affected parents
• 50% affected to have affected child

Question 7

Huntington’s disease

Answer 7

• Autosomal dominant
• Jerky movements, personality changes, deterioration, early deat
• Late onset disease
• Abnormal repeating of CAG repeats (36-125)

Question 8

Familial Hypercholesterolaemia (FH)

Answer 8

• Autosomal dominant
• High chloestral levels in blood
• Chloestral build up in joints
• Cardiovascular disease
• Treated by chloestral lowering drug and low chloestral diet
• Caused by lack of low density lipoprotein receptor (LDL) which removes extra chloestral

Question 9

Sex-linked recessive pedigree

Answer 9

• Females are carriers, mostly males affected
• Affected males transmit to daughters
• Carrier female will transmit to 50% of sons and 50% of daughters

Question 10

Haemophillia

Answer 10

• Sex-linked recessive
• Uncontrolled bleeding, extensive bruising, bleeding into joints
• A type - Factor Viii mutation, 1 in 5000 males
• B type - Factor iX mutation, 1 in 30,000 males

Question 11

Duchenne Muscular dystrophy

Answer 11

• Sex-linked recessive
• Muscle-wasting disease
• 1 in 35,000 males
• Dystrohpy gene mutation
• Dyrophin is very large so prone to mutations
• Dystrohpin connects cytoskeleton of a muscle fibre to extracellular matrix