Genetics

Question 1

what is mendelian disease

Answer 1

one that is controlled by a single locus in an inheritance pattern, a mutation in a single gene that is inherited

Question 2

Describe ALS in terms of genetics

Answer 2

mutation of SOD1 gene (the gene responsible for controlling excitotoxity)

Question 3

Amyloid Hypothesis of Alzheimer’s

Answer 3

• Amyloid precursor protein
• gene on chromosome 21
• mutations alter the process and increase production of beta amyloid
• only happens for inheritance in early onset Alzheimer’s

Question 4

How can a chromosome structure become abnormal

Answer 4

• duplication
• inversion
• deletion
• insertion
• translocation

Question 5

Describe chromosome aneuploidy

Answer 5

• occurs in >5% of pregnancies
• most often trisomy or occasional monosomy
• can involve all chromosomes but then wouldn’t make it past life
• autosomal triosomes: 21, 13, 18
• monosomy X - there are a number of aneuploidies associated with sex chromosomes

Question 6

which human characteristics follow Mendel’s first law

Answer 6

• phenylketonuria
• huntington’s disease
• achondroplasia
• cystic fibrosis
• sickle cell disease

Question 7

What is an example of a sex-linked recessive disorder

Answer 7

Hemophilia B - blood clotting disorder causing easy bruising and bleeding

inherited mutation of gene for factor IX, deficiency of factor IX

Question 8

What causes x-linked red/green colour blindness

Answer 8

mother to son passing the mutation on the 23rd chromosome

Question 9

Describe non-mendelian inheritance

Answer 9

• mechanism where inheritance does not follow normal patterns
• e.g. mitochondrial inheritance (faulty energy production) - may cause muscle disorders (parkinson’s)

Question 10

Describe epigenetics

Answer 10

• inheritance through a change in gene expression without a change in genetic code

Question 11

Genetics - MND

Answer 11

• SOD1 mutation

- C9orf72 mutation (hexonucleotide repeat in gene of unknown function, expansion of 6 bases)

Question 12

Genetics - Huntington’s disease

Answer 12

• mutated HTT gene
• Tri nucleotide repeat
• repeat expansions of CAG (codon for glutamine)
• 0ver 60 repeats in early onset
• < 27 repeats = unaffected
• repeat expands through generation (onset gets earlier)