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My MCD- Genetics > Lecture 3- More stories from the genetics clinic > Flashcards

Lecture 3- More stories from the genetics clinic Flashcards

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Biology 101 flashcards
1
Q

What is epigenetic modification? (w.r.t. DNA methylation)

A
  • No change in genetic sequence
  • DNA methylation- addition of methyl group to 5’ of pyramiding ring of cytosine
  • occurs in humans at CpG dinucleotides
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2
Q

What does methylation at the gene promoter cause?

A

Represses gene transcription

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3
Q

What is genomic imprinting?

A
  • Non-mendelian inheritance

- the genome carries an imprint or ‘stamp’ of its parental origin

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4
Q

What causes genomic imprinting?

A

DNA methylation and epigenetic modification

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5
Q

List two example of genetic imprinting disorders

A 
Prader-WIlli (Paternal)
Angelman syndrome (Maternal)
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6
Q

What are the symptoms of Prader Willi syndrome?

A 
Hyperphagia --> obesity
Mental impairment
Behaviuoral problems
Muscle Hypotonia
Shrort, stature, small hands and feet
Delayed/ incomplete puberty --> infertility
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7
Q

How is Prader-WIlli syndrome managed?

A
  • Diet restriction (hyperplasia)
  • Exercise to increase muscle mass (hypotonia)
  • GH treatment (short stature)
  • HRT (for delayed puberty)
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8
Q

What are the symptoms of Angelman syndrome?

A
  • development delay and speech impairment
  • movement disorder
  • Behavioural uniqueness (happy, excitable etc)
  • microcephaly
  • seizures
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9
Q

How is Angelman Syndrome diagnosed?

A
  • Clinica features and molecular diagnosis
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10
Q

What is the treatments for Angelman?

A

Symptomatic- anti-convulsant, physiotherapy, communication therapy

  • Normal life span
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11
Q

Describe the structure of the mitochondrial genome

A
  • 37 genes
  • Code for: tRNA, rRNA, respiratory complexes
  • circular DNA
  • 2-10 plasmids per mt
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12
Q

How are mitochondria inherited?

A

Through females via oocyte

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13
Q

Why can the phenotype of mitochondrial inheritance vary?

A

Heteroplasmy- cell contains diseased and non-diseased mitochondria

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14
Q

Give two examples of mitochondrial disorders

A

MELAS (mitochondrial encephalomyopathy, lactic acidosis and stroke like episodes)
LHON (Leber’s Hereditary Optic Neuropathy)

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15
Q

What are the symptoms of MELAS?

A 
Muscle weakness
Vomiting
Episodic seizures
Headache
Hemiparesis
Dementia
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16
Q

How is MELAS diagnosed and treated?

A

Muscle biopsy

Symptomatic treatment

17
Q

What is the genetic mechanism behind MELAS?

A
  • single mutation in several genes
    1) MTTL1: tRNA translates codon as Phe instead of Leu during mt protein synthesis
    2) MTND1, MTND5: NADH dehydrogenase subunits 1 and 5
18
Q

What are the symptoms of Lebers?

A
  • degeneration of retinal ganglion cells
  • Bilateral, painless, loss of central vision
  • Optic atrophy
  • average age of onset 20
  • more common in males
19
Q

How is Leber’s diagnosed?

A
  • ophthalmological findings

- Blood test for mtDNA mutations

20
Q

Which genes might be mutated in LHON?

A
  • MTND1, MTND4, MTND5, MTND6: NADH dehydrogenase subunits

- Cytochrome B MTCYB

21
Q

Which genetic diseases are newborns screened for and how?

A

Heel prick test

  • Sickle cell diseas
  • Cystic fibrosis
  • Congenital hypothyroidism
  • Phenylketonuria
  • MCADD
22
Q

What are the symptoms of phenylketonuria?

A
  • lack of melanin
  • eczema, musty odour (excess of phenyl acetate)
    Can lead to:
  • seizures
    -severe mental retardation
23
Q

What causes the lack of melanin in PKU?

A

Tyrosine deficiency

24
Q

What causes severe mental retardation in PKU?

A

Phenylalanine hydroxylase deficiency –> Phenylalanine accumulation–> converted to phenylpyruvic acid –> excreted in urine

25
Q

What is the treatment for PKU?

A
  • early detection
  • remove Phenylalanine from diet
  • protein supplements to supply other amino acids
  • strict diet in pregnancy
26
Q

What are the symptoms of MCADD?

A
  • Episodic hypoketotic hypoglycaemia
  • Vomiting, coma, metabolic acidosis, encephalopathy
  • 25% mortality if undiagnosed
27
Q

What is the treatment for MCADD?

A
  • avoid fasting

- nutritional supplements

My MCD- Genetics (6 decks)

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