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IMS > Genetic Variation > Flashcards

Genetic Variation Flashcards

1
Q

What are Mutations?

A

hereditable change in the base sequence of genes

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2
Q

What are Genetic Variations?

A

Arise from Mutations that are positively selected described as DNA polymorphism

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3
Q

What is DNA polymorphism?

A

Any difference in Nucleotide sequence

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4
Q

What are the 5 reasons Mutations can arise?

A
  1. Strand breakage - lose nucleotides
  2. Base loss - broken glycosidic bond
  3. Base change - guanine is oxidised
  4. DNA crosslinking - UV light
  5. DNA replication error - errors not corrected
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5
Q

What happens when DNA repair mechanisms fail?

A

Leads to genetic damage

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6
Q

What are the health consequences for DNA not being repaired?

A
  1. Cancer susceptibility
  2. Progeria
  3. Neurological defects
  4. Immunodeficiency
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7
Q

Why do changes in DNA most commonly arise from?

A

Errors in DNA replication

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8
Q

What is the Mutation Rate?

A

If it is too low organisms cant adapt, if it is too high information cant be retained

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9
Q

What has the highest mutation rate?

A

Mitochondrial Genome

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10
Q

How does Genetic Variation arise?

A

As a consequence of mutation - Recombination (crossover events in meiosis)

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11
Q

What are the 3 Types of Mutations?

A
  1. Point Mutations
  2. Insertions/Deletions
  3. Chromosomal Mutations
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12
Q

What is a Point mutation?

A
  • Changes to a single nucleotide (substitutions)

- Missense and nonsense mutations

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13
Q

What is a Chromosomal mutation?

A
  • Polyploidy - multiple sets of chr
  • Aneuploidy- abnormal number, extra/missing chr
  • Chromosome rearrangements - parts moved to other chr
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14
Q

What is a Missense mutation?

A

A change in nucleotide sequence that results in a change to AA sequence

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15
Q

What types of Missense mutations are they?

A

Point mutations
Frameshifts
Loss of function (PAH) Gain of function (Achondroplasia)
Could effect protein function

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16
Q

What is a Nonsense mutation?

A

A change in nucleotide sequence that results in premature stop codon caused by point mutations and frameshifts

17
Q

What does Nonsense mutations result in?

A

Non-functional protein
PAH mutation in BMPR2 gene
Duchenne muscular dostrophy- dystrophin gene

18
Q

What are Insertions/Deletions?

A 
Remove 1 to millions of nucleotides
5-10% all mutants
50% DMD
frame shift
a-thalassemias associated with melenoma
19
Q

What Instrument can you Identify Gene mutations on?

A

Electropherogram

20
Q

What are the features of Pulmonary Arterial Hypertension?

A

Intimal fibrosis
Direction of blood flow
Media thickening

21
Q

What are Expanding trinucleotide repeats?

A

Simple tandem repears, during replication increase in copy number
- 17 diseases include huntingtons diseas

22
Q

What happens in Huntington Disease?

A
  • CAG repeats encode a poly-glutamine region
  • In IT15 gene encoding huntington protein consists of 6-35 repeats
  • 36 or > causes neurodegenerative disease
  • raises ethical issues during genetic screening
23
Q

What are Transposons?

A

Sequence of DNA that can move around the genome act as recombination hotspots

24
Q

What are the 3 Types of Transposons?

A

Retrotransposonss - ‘copy and paste’
DNA transposons - ‘cut and paste’
Alu Repeats- most abundant, in LDL receptor for pathogenic deletions, also removes bad cholesterol eg FH

25
Q

What is an advantage of Selective pressure in a Malaria case?

A

Selective pressure for erythrocytes with sickle cell haemoglobin mutation can provide protection against malaria

26
Q

What is the distinct characteristics Cancers acquire in mutations?

A

Mutations are selected as they proliferate more and accelerate mutation rate

27
Q

What is Haploinsuffiency?

A

we all have 2 copies of a gene (diploid) , this is when one copy is deleted or inactivated by a mutation so only one copy is functioning

28
Q

What Happens in Haploinsuffiency?

A
  • The loss of function mutation tends to be recessive for 2 reasons - feedback loops & 50% gene sufficient
  • dosage effect may be seen as gene part of signalling system and competes to determine metabolic switch
  • gene products need a&b globin to make thalassemia (anaemia)
29
Q

What is Human Genetic Variation?

A

single nucleotide changes where 25% are structural changes in copy numbers

30
Q

What is Penetrance?

A

how frequently the disease is manifested

IMS (53 decks)

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