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MCD: GENETICS > Genetics 3 (Genetics Clinic) > Flashcards

Genetics 3 (Genetics Clinic) Flashcards

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Biology 101 flashcards
1
Q

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

A
  • Paternal: hydatidiform mole
  • Maternal: ovarian teratoma
  • origin of parental DNA is important
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2
Q

What is the mechanism of imprinting?

A

DNA Methylation

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3
Q

Which base gets methylated?

A

5’ position on the pyrimidine ring of cytosine

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4
Q

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

A

Repressed gene transcription

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5
Q

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

A

Chromosome 15

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6
Q

What are some symptoms of Praeder-Willi Syndrome?

A
  • Hyperphagia
  • Obesity
  • Mental Retardedness
  • Short Stature
  • Hypotonia
  • incomplete puberty and Infertility
  • small hands and feet
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7
Q

What are some symptoms of Angelman Syndrome?

A
  • Microcephaly
  • speech impairment
  • movement disorder
  • behavioural uniqueness
  • developmental delay
  • seizures (<3 yrs)
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8
Q

How does uniparental isodisomy lead to Prader-Willi and Angelman Syndrome?

A
  • Non-disjunction in meiosis 2 makes gamete with two copies of chromosome 15 resulting in a zygote with three copies of chromosome 15
  • Failure to remove duplicated chromosome results in zygote having two copies of chromosome 15 from same parent
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9
Q

What is heteroplsmy?

A

situation within single cell where there’s a mixture of mitochondria, some containing mutant DNA and some containing normal DNA

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10
Q

What are two examples of mitochondrial disease?

A
  • MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis & stroke)
  • LHON (Leber’s hereditary optic neuropathy)
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11
Q

What are some symptoms of MELAS?

A
  • muscle weakness
  • vomiting
  • dementia
  • episodic seizures
  • headache
  • hemiparesis
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12
Q

What is MELAS and what mutations cause it?

A
  • progressive neurogenerative disorder
  • MTTL1 (tRNA translates codon as Phenylalanine instead of leucine)
  • MTND1 and MTND5 (NADH Dehydrogenase subunits 1 and 5)
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13
Q

Which gender is more affected by LHON and what are some symptoms of it?

A
  • more common in males

- Painless bilateral loss of central vision leading to blindness

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14
Q

Which gene mutations cause LHON?

A
  • MTND1, 4,5 and 6 (NADH Dehydrogenase subunits 1, 4, 5 and 6)
  • MTCYB (cytochrome B)
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15
Q

What are two examples of inborn errors of metabolism.?

A
  • Phenylketonuria

- MCAD deficiency

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16
Q

What are some symptoms of Phenylketonuria?

A
  • Mental retardation
  • Blonde hair/blue eyes (reduced melanin)
  • Eczema
17
Q

How is phenylketonuria detected?

A

Elevated levels of phenylalanine in the blood

18
Q

What is the treatment for PKU?

A
  • early detection
  • Remove phenylalanine from diet
  • protein supplements given
  • strict diet in pregnancy
19
Q

What is a common feature of MCAD Deficiency?

A

Episodic Hypoketotic Hypoglycaemia

20
Q

What is the treatment for MCAD Deficiency?

A

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

21
Q

What is the difference between Angelman and Praeder-Willi Syndromes in terms of chromosomes?

A
  • Praeder Willi: loss of paternal chromosome

- Angelman: loss of maternal chromosome

22
Q

What is the management of Praeder-Willi Syndrome?

A
  • diet restriction
  • exercise to increase muscle mass
  • GH for short stature
  • hormone replacement
23
Q

What is the management of Angelman Syndrome?

A
  • anticonvulsant
  • physiotherapy
  • communication therapy
24
Q

How are diagnoses made for MELAS and LHON?

A
  • MELAS: muscle biopsy

- LHON: ophthalmological findings and blood tests for mtDNA mutation

25
Q

Which gene has a mutation for MCADD?

A

ACADM gene

26
Q

What is the mitochondrial genome?

A
  • 37 genes encoding resp complexes, tRNA and rRNA

- 2-10 copies per mitochondrion

27
Q

What is mitochondrial inheritance?

A
  • female transmission from oocyte
  • males and females affected
  • phenotype variable due to heteroplasmy
28
Q

What 3 features are part of the UK newborn screening programme?

A
  • physical exam
  • hearing test
  • blood spot test for MCADD and PKU

MCD: GENETICS (7 decks)

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