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1

The loss of function of a gene on which chromosome causes Prader-Willi and Angelman Syndrome?

Chromosome 15

2

State some symptoms of Prader-Willi Syndrome

Hyperphagia
Obesity
Mental Retardedation
Short Stature
Hypotonia
Infertility

3

State some symptoms of Angelman Syndrome.

Microcephaly
Poor or absent speech
Gait ataxia
Severe developmental delay

4

What is the general effect of methylation on the gene promoter?

Repressed gene transcription

5

What phenomenon determines the severity of mitochondrial disease?

Heteroplasmy

6

Which base gets methylated?

5’ position on the pyrimidine ring of the cytosine

7

State two examples of mitochondrial disease

MELAS (Mitochondrial Encephalomyopathy, Lactic Acidosis and Stroke like episodes) and LHON (Leber's Hereditary Optic Neuropathy) Loss of central vision. There's also MIDD (Maternally inherited Diabetes and Deafness).

8

How is phenylketonuria detected?

Elevated levels of phenylalanine in the blood.

9

What are the three possible causes of Prader-Willi and Angelman Syndrome?

Deletion of the PWS/AS critical region on chromosome 15
Uniparental isodisomy
Other mechanisms e.g. translocations

10

What is the treatment for PKU?

Remove phenylalanine from the diet

11

What is a common feature of MCAD Deficiency?

Episodic Hypoketotic Hypoglycaemia

12

What is the treatment for MCAD Deficiency?

Maintain adequate calorie intake to prevent the body from switching to beta-oxidation.

13

Describe how uniparental isodisomy can lead to Prader-Willi and Angelman Syndrome.

Non-disjunction in meiosis 2 makes a gamete that has two copies of chromosome 15 resulting in a zygote with three copies of chromosome 15. Failure to remove the duplicated chromosome results in the zygote having two copies of chromosome 15 from the same parent.

14

What happens if the full genome of an embryo derives from one parent and what is the significance of this finding?

Paternal – hydatidiform mole
Maternal – ovarian teratoma
Shows that the origin of the parental DNA is important

15

Mutations in what genes cause LHON?

MTND1, 4,5 and 6 – NADH Dehydrogenase subunits 1, 4, 5 and 6
MTCYB – cytochrome B

16

A mutation in which gene causes MCAD Deficiency?

ACADM

17

What mutations cause MELAS?

MTTL1 – tRNA translated codon as Phenylalanine instead of leucine
MTND1 and MTND5 – NADH Dehydrogenase subunits 1 and 5

18

How is PWS and AS diagnosed? Which genes near/in the PWS/AS critical region are used?

FISH – fluorescence in situ hybridisation
PML (promyelocytic leukaemia) gene is just outside the PWS/AS critical region snRNP (small nuclear ribonucleoprotein) gene is inside the PWS/AS critical region

19

Give two examples of inborn errors of metabolism.

Phenylketonuria and MCAD deficiency

20

State some symptoms of Phenylketonuria

Mental retardation
Blonde hair/blue eyes
Eczema

21

What is the mechanism of imprinting?

DNA Methylation