MGD mutations (session 9) Flashcards Preview

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1
Q

what causes mutations?

A

ionising radiation
intercalating agents
DNA slippage
tautomeric shift

2
Q

how does ionising radiation cause mutation? what is an example of ionising radiation?

A

UV radiation causes thymine dimmer formation
(UV causes bases on the same strand of DNA to bind to itself)
e.g. X-ray in diagnostic medicine

3
Q

how does intercalating agents cause mutations?

A

intercalation of chemical IQ (ethidium bromide) between bases (forcing itself onto DNA strand), pushing bases apart, causing misreading by DNA polymerase, and therefore deletion of single base

4
Q

how does tautomeric shift cause mutations?

A

a proton briefly changes position ‘rare form’ causing altered template base in DNA replication, therefore DNA polymerase attaches different complementary base (to rare form), only 25% being the complimentary base
(proton moves)

5
Q

how does DNA slippage cause mutations?

A

looping out of template or building strand to cause insertions or deletions

base loop out of new strand = 1 extra base in new strand
base loop out of template strand = 1 less base on new strand

6
Q

what are the 2 different types of DNA damage that can occur?

A

single stranded damage

double stranded damage

7
Q

what happens in single stranded damage repair for nucleotide excision repair? an example of this?

A

e.g. UV damage

removal of a longer region of damaged DNA and replacement

8
Q

what happens in single stranded damage repair for mismatch repair?

A

patching up mistakes made by DNA polymerase

9
Q

what happens in single stranded damage repair for base excision repair?

A

removes JUST the faulty base and replacing them

remove a nitrogenous base and replacing it

10
Q

what are the 3 types of single stranded DNA damage repair?

A

nucleotide excision repair
mismatch repair
base excision repair

11
Q

what are the 3 types of double stranded DNA damage repair?

A
  1. homologous recombination
  2. non-homologous end joining (NHEJ)
  3. microhomology-mediated end joining (MMEJ)
12
Q

what is homologous repair in double stranded DNA damage?

A

using the other chromosome as a template for repair (in a pair of homologous chromosomes)

13
Q

what is non-homologous end joining (NHEJ) repair in DNA damage?

A

ligation of the DNA breaks using micro-homologous regions

14
Q

what is microhomology-mediated end joining (MMEJ)?

A

small homologous regions used to align DNA regions

15
Q

what is a point mutation?

A

a single, isolated nucleotide base

16
Q

what are the different types of point mutations?

A
  1. nonsense
  2. missense
  3. silent
17
Q

what is nonsense mutation?

A

a single nucleotide mutation which results in the insertion of a stop codon in the transcript

18
Q

what is missense mutation?

A

single nucleotide mutation which result in a change of amino acid
the effect of the change depends on the properties of the amino acids involved e.g. change on DNA or mRNA and which gene

19
Q

what is silent mutation?

A

point mutations which have no effect on the amino acid coded

but can affect mRNA splicing introns –> can lead to heritable diseases

20
Q

what is a transition mutation?

A

e.g. purine –> purine (2 rings - A & G)

21
Q

what is a transversion mutation?

A

e.g. purine –> pyrimidine (1 ring - C,T,U)