monogenic diseases

Question 1

autosomal dominant effect

Answer 1

caused by toxic protein; 1 affected parent, vertical transmission, 50% risk affected child

Question 2

autosomal dominant examples

Answer 2

Huntington’s, osteogenesis imperfecta, FH, achondroplasia

Question 3

genetic anticipation definition

Answer 3

age of onset decreases, severity increases, may be due to unstable expansible triplet repeat

Question 4

Huntungton’s: biochemistry

Answer 4

expansion of trinucleotide CAG in gene coding for Huntingtin

Question 5

autosomal recessive effect

Answer 5

caused by absence of functional protein; no affected parent. usually no family history, 25% risk affected child

Question 6

autosomal recessive: cystic fibrosis as an example

Answer 6

CFTR (ATP-dependent chloride channel) maps to 7q31; mutation in delta F508; treated with physiotherapy

Question 7

X-linked recessive effect

Answer 7

no affected parent, transmitted by female carrier, only affects males, sons have 50% chance affected, daughters have 50% chance carrier

Question 8

X-linked recessive examples

Answer 8

haemophilia, DMD (muscle degeneration caused by absence of dystrophin; shorter survival rate than BMD)

Question 9

co-dominance definition

Answer 9

both mutated and normal genes present