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Medical Cell Biology and Genetics > L21- DNA/ chromosomal mutations > Flashcards

L21- DNA/ chromosomal mutations Flashcards

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1
Q

mutagenesis

A

the process of mutation generation

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2
Q

a mutation is

A

a change of the nucleotide sequence, which can either have no affect on protein structure, or can render a protein changed

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3
Q

mutations arise

A

spontaenously due to mutagens

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4
Q

spontaneous mutations e.g.

A

deamination mutations

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5
Q

example of deamination

A

changes Cytosine to Uracil

e.g. can change 5-methylcytosine to thymine

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6
Q

types of mutagens

A

exogenous

endogenous

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7
Q

endogennous

A

DNA replication defects

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8
Q

exogenous

A
  • ionsing radiation
  • free radical
  • mutagenic chemicals e.g. nitrites
  • anti cancer agents
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9
Q

Defective or error prone DNA repair leads to

A

mutation

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10
Q

mutations may or may not

A

cause phenotypic cahnge

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11
Q

mutations can be

A

good or bad

  • source of genomic variation
  • driving force of evolution
  • may cause disease
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12
Q

in transcription …

  • DNA is read ……..
  • mRNA is synthesised ……
A
  • DNA is read 3’ to 5’
  • mRNA is synthesised 5’ to 3’
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13
Q

In translation….

  • mRNA is read…….
  • polypeptide synthesis……
A
  • mRNA is read 5’ to 3’
  • polypeptide synthesis N to C
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14
Q

types of mutations

A

small scale (micro)

large scale (macro)

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15
Q

small scale mutations (3)

A
  • substitution
  • deletion
  • insertion
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16
Q

large scale mutations (macro)

A
  • abnormal number of chromosomes
  • structural abnormalities
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17
Q

Abnormal number of chromosomes e.g.

A
  • aneuploidy
  • polypoloidy
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18
Q

structural abnormalities (4)

A
  • deletions
  • duplication
  • inversion
  • translocation
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19
Q
A
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20
Q

a transposable element (transposome)

A

is a DNA sequence that can change position within a genome- creating or reversing mutations

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21
Q

transposable elements are what sort of source of mutagenesis

A

endogenous

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22
Q

DNA sequences of transposable elements

A
  • supernumerary (many copies)
  • specific
  • always contain within other DNA molecule
  • moves as a discrete unit
  • moves to random sites
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23
Q

transposable elements insertionally

A

inactivate genes or change gene expression

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24
Q

TEs can insert (jump into) a gene to

A

inactivate it

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25
Q

TE can jump out of a gene to

A

reactivate it

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26
Q

TE and the size of the gene

A

The bigger the gene the more likely it will be inactivated

e.g. Hb gene very small- unlikely

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27
Q

TE can also jump into

A

regulatory regions- affecting DNA expression

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28
Q

cartoon of transpostion

A
29
Q

small scale mutations are synonymois with

A

single nucleotide polymorphism (SNP)

30
Q

types of SNP

A
  1. Indels
  2. substitution of a single. few nucleotides within a gene
31
Q

Indels

A

deletion or insertion mutations

32
Q

deletion

A

nucleotide is removed from DNA

33
Q

Insertion

A

nucleotide is inserted into DNA

34
Q

INDELs can cause

A

frameshift mutations

35
Q

If a multiple of three nucleotides are removed

A
  • non frameshift mutation ( change in polypeptide length)

Reading frame displaced an entire codon- remaining amino acids unchanged- similar resulting protein

36
Q

If one nucleotide is added or removed

A
  • frameshift mutation

Resulting protein abnormally long or short, with random amino acids

Most likely unfunctional

37
Q

substitution mutation

A

one nucleotide is replaced by another

38
Q

substitution mutations may result in

A

silent mutations (synonynous)

missense jutation

nonsense mutations

39
Q

synonymous (silent) mutations

A

same amino acid- degenerative genetic code

40
Q

missense mutation

A

mutation codes for a different amino acid

  • depends where the mutations occurs:
  • can result in functional protein
  • can result in non-functional protein
41
Q

nonsense mutation

A

stop codon

  • most deleterious
42
Q

transition mutation (substitution mutation)

A

substition of the same base type

e.g. purine to purine

43
Q

transversion (substitution)

A

change to diff type of base

i.e. pyrimidines to purine

44
Q

pyrimidines

A

urine

cytosine

thymine

45
Q

purines

A

guanine

adenine

46
Q

example of single nucleotide polymorphism disease (SNP)

A

sicke cell mutation

47
Q

sicke cell mutation

A
  • Mutation in codon 7 of HBB gene
  • Base substitution mutation (missense)
  • One amino acid changed (6th aa- first is start codon)
48
Q

SNP mutatons within regulatory sequences

A
  • Alter. Promotor activity
  • Alter translation initiation at AUG
  • Prevent mRNA splicing
  • Reduce mRNA stability
49
Q

structural abnormalities

A

Movement of sections of chromosome

  1. deletion
  2. duplication
  3. inversion
  4. translocation
50
Q

abnormal number of chromosomes occur due to

A

errors in gamete formation e.g. nondijunction

51
Q

deletion

A

part of the gene is missing

52
Q

duplication

A

part of the chromosome is duplicated

53
Q

inversion

A

part of the chromosome breaks of and reattaches

54
Q

translocation

A

parts of the chromosome are switched

55
Q

Robertsonian translocation

A
  • P arms detach from two chromosomes and are discarded
  • Both Q arms from the chromosomes fuse
56
Q

individuals with robertsonian translocation only have

A

45 chromosomes

57
Q

aneuploidy

A

loss or gain of whole chromosome due to non-disjunction disorders

e.g. trisomyn and monosomy

58
Q

trisomy

A

additional chromosome e.g. downsyndrome

59
Q

monosomy

A

missing chromosome e.g. Turners syndrome

60
Q

polyploidy

A
  • Increased number of chromosomes per set
  • E.g. Gain of haploid set of chromosomes (3n=69)
61
Q

most common cause of polyploidy

A

polyspermy

62
Q

triploidy occurs in how many oregnanacies and is the ause of how many miscarriages

A

2-3%

15% of miscarriages

63
Q

moscaicism

A

Presence of two or more cell lines in an individual (throughout the body or tissue- specific)

Caused by non-disjunction in mitosis

64
Q

detecting mutatiosn in chromosome suses

A

cytogenetic testing

65
Q

name 4 cytogenetic tests

A

E.g. karyotyping (old fashioned)

E.g. Fluorescent in situ hydrbidsaiton (FISH)

E.g. microarray hydbridation

E.g. DNA sequencing

66
Q

why is cytogenetic testing important

A
  • accurate diagnosis and prognosis of clinical problems
  • better clinical management
  • assess future reproductive risk
  • prenatal diagnosis
67
Q

who should be refereed to cyrtogenetic testing

A

Prenatal diagnosis

Birth defects

Abnormal sexual development

Infertility

Recurrent fetal loss

Leukaemia

Solid tumours

Prognostic info for specific translocations

68
Q

balanced mutations

A

no genetic info is lost or no phenotypic changes are apparent

69
Q

unbalanced mutatuons

A

Anything that’s not balanced = unbalanced

◦E.g. loss of genetic info or gain of genetic info

◦Chain in phenotype

Medical Cell Biology and Genetics (33 decks)

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