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Y1 - MCD > Genetics 2-3 > Flashcards

Genetics 2-3 Flashcards

1
Q

What is a polymorphism?

A

A mutation present in more than 1% of the population.

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2
Q

What are the features of a monogenic genetic disorder?

A
  • Clear pattern of inheritance
  • No environmental influence
  • Rare
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3
Q

What are the features of a complex genetic disorder?

A
  • Common
  • Environmental and genetic influences
  • No clear pattern of inheritance
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4
Q

What is a missense mutation?

A

Single changed nucleotide resulting in a different amino acid being formed and therefore a malfunctioning protein. Known as a point mutation.

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5
Q

What is a nonsense mutation?

A

Single changed nucleotide resulting in a shorter protein due to a stop codon being coded for. Known as a point mutation.

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6
Q

What are insertion and deletion mutations examples of?

A

Frameshift mutations

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7
Q

What is incomplete penetrance?

A

Symptoms are not always present in an individual with a disease-causing mutation.

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8
Q

What is variable expressivity?

A

The severity of a disease between individuals with the same disease-causing mutation may vary.

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9
Q

What is meant by phenocopy?

A

Having the same disease but different underlying cause.

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10
Q

What are dominant conditions associated with?

A

Presence of a toxic protein so require switching off of that mutant gene.

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11
Q

What are recessive conditions associated with?

A

Absence of a functional protein so restoring the function of this protein is often needed.

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12
Q

What is genetic imprinting?

A

Genes are expressed differently according to whether they are inherited from the mother or the father.

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13
Q

What is uniparental isodisomy?

A

When the zygote has all the genetic information from only one parent.

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14
Q

What does maternal uniparental isodisomy result in?

A

Ovarian teratoma

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15
Q

What does paternal uniparental isodisomy result in?

A

Hydatidiform mole

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16
Q

What is the mechanism underlying genetic imprinting?

A

DNA methylation

17
Q

What is DNA methylation?

A

The addition of a methyl group to the 5th position on the pyrimidine rings of cytosine.

18
Q

What is Prader Willi syndrome?

A

The paternal deletion of a part of chromosome 15, resulting in obesity, short stature, infertility, delayed puberty, mental impairment and behavioural problems.

19
Q

What is Angelman syndrome?

A

The maternal deletion of a part of chromosome 15, resulting in development delay, speech impairments, “happy demeanour” , movement disorder (gait ataxia), microcephaly and seizures.

20
Q

How is mitochondrial DNA passed on?

A

Via the ovum. The mitochondria in the sperm is lost after fertilisation - only the DNA is transferred to the ovum.

21
Q

How big is the mitochondrial genome?

A

16.6kB and 37 genes

22
Q

What is heteroplasmy?

A

A mixture of normal and mutant mitochondria present in the same cell. The severity of a disease is dependent on the ratio of affected and unaffected mitochondria.

23
Q

How many mitochondria are affected to cause no disease?

A

Up to 3

24
Q

How many mitochondria are affected to cause a mild disease?

A

5

25
Q

How many mitochondria are affected to cause a severe disease?

A

9

26
Q

What enzyme is involved in methylation of cytosine?

A

DNA methyltransferase (DNMT)

27
Q

What affects methylation patterns?

A

Environment, age and the type of tissue.

28
Q

What are two examples of mitochondrial disorders?

A

LHON - Leber’s heriditary optic neuropathy

MELAS - mitochondrial myopathy, encephalophathy, lactic acidosis and stroke

29
Q

What are the symptoms of LHON?

A
  • Onset between 20s and 30s
  • More common in males
  • Bilateral and painless loss of vision leading to blindness
30
Q

How is LHON diagnosed?

A

mtDNA analysis or ophthalmological findings.

31
Q

What is the mutation associated with LHON?

A

90% are associated with NADH dehydrogenase or cytochrome B mutations.

32
Q

What are the symptoms of MELAS?

A
  • Vomiting and diarrhoea
  • Muscle weakness
  • Seizures
33
Q

What is affected in MELAS?

A

Muscle and brain most severely due to high metabolic demands (therefore lots of affected mitochondria). Due to phenylalanine being produced instead of leucine.

34
Q

What is chronic myeloid leukaemia caused by?

A

Chromosomal translocation/fusion of chromosomes 9 and 22 resulting in the Philadelphia chromosome.

35
Q

What happens in CML?

A

Translocation results in production of MCR-ABL1 tyrosine kinase being produced, resulting in overproduction of mature blood cells (granulocytes).

36
Q

How is CML treated?

A

BCR-ABL1 tyrosine kinase inhibitors

37
Q

What is acute promyelocytic leukaemia caused by?

A

An accumulation of immature granulocytes (promyelocytes)

38
Q

What genetic change caused promyelocytic leukaemia?

A

A translocation of the RAR-a gene on Chr17 to PML gene on Chr15, forming PML-RAR-a protein which binds strongly to DNA and blocks transcription.

Y1 - MCD (38 decks)

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