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IMS- Strand 1 > Gene Mutations > Flashcards

Gene Mutations Flashcards

1
Q

What is a gene mutation?

A

an alteration in the nucleic acid sequence of the genome of an organism

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2
Q

How do gene mutations arise?

A
  • Errors during replication
  • Mutagens
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3
Q

What errors occur during replication?

A
  • Point mutations
  • Replication slippage
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4
Q

What does Ultraviolet cause?

A
  • causes dimerization of adjacent pyrimidine bases (esp thymines)= deletion mutation
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5
Q

What is dimerization?

A

the process of joining two identical or similar molecular entities by bonds

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6
Q

What does ionising radiation cause?

A

Electromagnetic waves and particles= direct and indirect damage

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7
Q

What is an example of indirect damage caused by ionising radiation?

A

Free radicals which attach to DNA strand and break pieces off

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8
Q

What chemicals are classed as mutagens?

A

asbestos
cyanide
alcohol
sawdust
disinfectant

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9
Q

What are the general approaches against mutation?

A

1- Prevent
2- Repair
3- Give up (apoptose the whole cell)

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10
Q

What does prevent involve?

A
  • Melanin (protect DNA in skin)
  • Peroxisomes (an organelle that makes antioxidant enzymes)
  • Good life choices
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11
Q

What does repair involve for Nicks? (mutagens)

A

phosphodiester bond breaks which DNA ligase repairs

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12
Q

What does repair involve for single stranded damage to bases? (mutagens)

A

base excision repair for small bits of damage and nucleotide excision repair for big bits of damage

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13
Q

What does Polymerase III do to repair mutations caused during DNA replication?

A

Proofreading activities

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14
Q

What other form of repair is there if mutation is caused by DNA replication?

A

Mismatch repair, 4 proteins detect lack of hydrogen bonds between mismatched base pairs, and then repair

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15
Q

What 4 proteins are involved in mismatch repair?

A

MSH2
MSH6
MLH1
PMS2

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16
Q

Why is giving up sometimes the best option?

A

There may be too many mutations for cells to repair
Apoptosis (programmed Cell death) is initiated

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17
Q

Examples of giving up

A
  • Sunburn with blistering
  • Radiotherapy treatment
  • Radiation sickness
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18
Q

How does the location of mutation affect outcome?

A

Non-coding= no affect
Coding= potential for effect

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19
Q

What is frameshift?

A

Shifts reading frame (rest of protein effected), caused by insertion or deletion of non multiples of 3

20
Q

What is a silent mutation?

A

different base, but still codes for the same amino acid so no effect

21
Q

What is a Missense mutation?

A

changes to a different amino acid, only affects one amino acid so small effect especially if similar shape/ charge

22
Q

What is a nonsense mutation?

A

changes codon to a stop codon, big effect if at start of protein

23
Q

How can a mutation cause cancer?

A

Mutation in gene that normally controls cell division
oncogenes or tumour supressor genses= potential to cause cancer

24
Q

What are Germline cells?

A

cells in body that make sperm and eggs

25
Q

What are somatic cells?

A

All other body cells

26
Q

How can a mutation effect the phenotype of offspring?

A

If mutation occurs on a relevant protein and in a germline cell= potential to change phenotype of offspring
Could be harmless change or cause a genetic disease
Possibility for selective advantage

27
Q

What is Cystic Fibrosis?

A

Autosomal recessive condition
Caused by one of many mutations in gene encoding the CFTR protein

28
Q

What is CFTR?

A

cystic fibrosis transmembrane conductance regulator

29
Q

What does CFTR do?

A

Is a membrane protein that transports chloride ions

30
Q

What happens if CFTR is defective?

A

Cl ions cannot exit cells
Sodium (thus water) follow Cl out of mucus into cell
Less water in mucus
thick mucus= recurrent infections

31
Q

What is Neurofibromatosis (NF)?

A

Autosomal dominant
Caused by a mutation in one of 2 genes

32
Q

In what protein can mutations occur to cause NF

A

Neurofibrin protein= NF1
Merlin protein= NF2

33
Q

What do NF1 & NF2 proteins control?

A

Control cell cycles as “tumour suppressor genes”

34
Q

What is the most common tumour for NF1?

A

Neurofibromas

35
Q

What is the most common tumour for NF2?

A

Schwannomas

36
Q

What is Phenylketonuria?

A

Autosomal recessive
Caused by mutation in the gene coding for the protein phenylalanine hydroxylase

37
Q

What is phenylalanine hydroxylase responsible for?

A

This enzyme is responsible for metabolising the amino acid phenylalanine

38
Q

Why is phenylketonuria variable?

A

Very dependant on early dietary modification
If phenylalanine free diet= near normal phenotype
If phenylalanine rich diet= build up in brain

39
Q

What is Huntington’s Disease?

A

Autosomal dominant
Affects men & women equally
Caused by increased CAG trinucleotide repeats in the gene that codes for huntingtin protein

40
Q

What age does huntington’s disease normally present?

A

30 to 50

41
Q

What is the huntingtin protein normally involved in?

A

Usually involved in transport along neronal axons

42
Q

Is Huntington’s disease variable and what are some symptoms?

A

-YES
progressive inability to control body movements
Change in mood/ personality
Symptoms are more severe and onset earlier with more CAG repeats
More CAG repeats occur with each generation

43
Q

Where is the huntingtin gene located?

A

short arm of chromosome number 4

44
Q

What are trinucleotide repeats?

A

A sequence of three bases repeated numerous times

45
Q

Why do trinucleotide repeats occur?

A

Due to slippage off DNA polymerase

46
Q

How will increased trinucleotide repeats in the huntingtin gene affect the huntingtin protein and cause symptoms?

A

An abnormally long version of the huntingtin protein is made, which doesn’t function properly and instead accumulates in neurons, disrupting the normal functions of these cells

47
Q

Why does Huntington’s show an increased severity and earlier onset every time it is passed down to subsequent generations?

A

The longer a trinucleotide CAG repeat is, the more unstable during replication. This means even more slippage of DNA polymerase will occur with each replication, elongating the gene further each time

IMS- Strand 1 (4 decks)

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