Week 8 Part 1

Question 1

X linked recessive

Answer 1

Affect sons
Daughters can be carriers because they can inherit the X chromosomes
If father is affected none of his sons are affected because they inherit his Y chromosomes
All the daughters are carriers because they inherit X chromosomes which are affected

Question 2

What are examples of X-linked Recessive?

Answer 2

Haemophilia A
X-linked severe combined immunodeficiency disorder (SCID)
Duchene muscular dystrophy
Becker muscular dystrophy

Question 3

X-linked dominant

Answer 3

Affected father: all daughters are affected, all daughters get X chromosomes
When affected daughters have offsprings, a 50% chance that their children have the disease
Chance is the same between 2 sexes
Affected sons have affected mother because they get Y chromosomes from their dad

Question 4

What are examples of X-linked dominant?

Answer 4

Retinitis pigmentosa (degenerative eye disease)
Chondrodysplasia Punctata (disorder of cartilage and bone development)
Hypophosphatemic rickets (bone deformity)

Question 5

Autosomal Recessive

Answer 5

Both parents are carriers, both sexes can be affected
25% that an offspring will be affected
Consanguinity - two cousins that are married, affected son
Homozygous - mutation will be the same on both chromosomes

Question 6

Examples of Autosomal recessive

Answer 6

Phenylketonuria (intellectual disability, seizures)
Tay-Sachs (deterioration of nerves + mental/physical abilities)
Hemochromatosis (iron overload)
Cystic fibrosis

Question 7

Autosomal dominant

Answer 7

Affected father - his offspring have 50% chance of being affected
It doesn’t skip generations unless there is a reduced penetrance

Question 8

What are examples of Autosomal dominant?

Answer 8

Huntington disease
Achondroplasia (short-limbed dwarfism)
Polycystic kidney disease
Werner mesomelic syndrome

Question 9

Y linked dominant

Answer 9

Not many genes on the Y chromosomes
Not many diseases
Inherited from father to son

Question 10

Examples of Y-linked dominant

Answer 10

Retinitis pigmentosa (degenerative rye disease)

Question 11

What is imprinting?

Answer 11

Epigenetic phenomonen by which certain genes are expressed in a parent-of-origin-specific manner

If the allele inherited from the father is imprinted, it is silenced and only the allele from the mother is expressed

Question 12

What are examples of Imprinting?

Answer 12

Beckwith-Wiedemann syndrome, large size and a predisposition to tumors

Prader-Willi syndrome

Angelman syndrome

Question 13

What is angelman syndrome?

Answer 13

Neuro-genetic disorder
Several different phenotypes - Ube3a gene
It is a ubiquitin ligand
Gene is expressed from maternally inherited chromosomes

Question 14

Mitochondrial

Answer 14

Inherited from mother, affected female

Her affected son will not pass it on because their children get mitochondria from unaffected mother

Question 15

What are examples of mitochondria?

Answer 15

Mitochondrial myopathy
Diabetes mellitus and deafness
Lebers hereditary optic neuropathy
Leigh syndrome, subacute sclerosing encephalopathy (brain lesions)