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Phase 1 - S1 Medical Cell Biology And Genetics > Errors Involving DNA > Flashcards

Errors Involving DNA Flashcards

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1
Q

What are oncogenes?

A

Genes that increase growth, promotes survival and inhibit apoptosis

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2
Q

Why might oncogenes have an increase in activity?

A

Due to mutation (either in the gene itself, in other involved signalling proteins or in the transcription factor binding region).

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3
Q

What are tumour suppressing genes?

A

Genes that inhibit proliferation, reduce growth or promote apoptosis

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4
Q

What is the p53 gene?

A

A tumour suppressing gene that is commonly mutated

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5
Q

What is slippage in DNA replication?

A

Where a newly synthesised nucleotide/strand can slip out and so there are extra nucleotides on the strand. Or nucleotides can slip out on the template strand, shortening the DNA strand.

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6
Q

What is mis-match pairing?

A

When DNA polymerase inserts the wrong nucleotide

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7
Q

How can a mismatch be easily repaired?

A

There can be a base excision repair from the exonuclease domain of the DNA polymerase.

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8
Q

What results from an increase of p53 activity?

A

Tumours

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9
Q

What is DNA replication stress?

A

Inefficient replication that leads to the replication fork slowing, stalling or breaking

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10
Q

What happens when the replication fork meets a single strand break?

A

A double strand break occurs

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11
Q

What disease results from a trinucleotide repeat?

A

Huntingtons

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12
Q

What is dysplasia?

A

Features of abnormal cell growth

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13
Q

Errors in what 4 areas lead to genomic instability?

A
  1. Errors in oncogenes
  2. Errors in tumour suppressing genes
  3. Errors in chromosome structure
  4. Errors in chromosome number
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14
Q

Increasing the activity of which genes results in dysplasia

A

Oncogenes

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15
Q

What is mismatch repair?

A

When DNA polymerase finds a mistake and so the exonuclease domain cuts out the mistake for polymerase to fix

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16
Q

Outline nucleotide excision repair

A

A stretch of damaged DNA is removed by endonuclease and replaced by DNA polymerase and joined together by DNA ligase, using a variety of proteins which are produced in the genes controlling this repair

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17
Q

What does UV light do to cells?

A

It initiates a reaction between 2 thymine molecule to form a pyrimidine dimer.

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18
Q

Why can some DNA synthesis inhibitors be used as antibiotics?

A

They may only inhibit bacterial DNA synthesis not human

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19
Q

What is non-homologous end joining used to repair

A

Double stranded breaks

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20
Q

Outline non-homologous end joining

A

The ends are directly lighted. This is done by proteins binding onto the ends of the breaks, which then recruit other proteins which removed damaged strands and then DNA ligase brings the strands together

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21
Q

What are chromosomal translocations?

A

When part of a chromosome attaches to another. It can be balanced or unbalanced

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22
Q

What is chromosomal inversion?

A

When a segment of DNA is reversed end to end.

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23
Q

What type of disease can be caused by translocations

A

Leukaemia

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24
Q

What is a mutation

A

An alteration in a gene or chromosome

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25
Q

What is a bulky addict

A

When chemicals bind to areas of DNA and prevent it replicating

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26
Q

When do mutations occur

A

When DNA repair mechanisms are defective

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27
Q

State exogenous sources of mutation

A

Ionising radiation, free radical, mutagenic chemicals

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28
Q

What are free radicals

A

Molecules with an extra electron

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29
Q

State endogenous sources of mutation

A

DNA replication defects and transposable elements

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30
Q

What are transposable elements

A

When DNA has no fixed position and move around the genome

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31
Q

What happens when a transposable element is inserted into a gene

A

It deactivates the gene

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32
Q

What is a mircomitation

A

Mutation involving one or few nucleotides

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33
Q

What is a macromutation

A

Mutation on chromosomes

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34
Q

What types of micromutations are there?

A

Deletions, insertions, substitutions

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35
Q

What types of macromutations are there

A

Deletion, duplication, inversion, substitution and translocation

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36
Q

What do deletions and insertions result in

A

Frameshift

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37
Q

What are missense mutations

A

Mutations resulting in a change in amino acid

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38
Q

What are silent mutations

A

Genes that give no change in amino acid

39
Q

What is a nonsense mutation

A

Mutation resulting in an early stop codon

40
Q

What types of mutations affect the amount of gene product

A

Mutations affecting translation or transcription

41
Q

How may mutations affecting splicing affect gene product

A

Mutations at the end of intron mean splicing sequences change so exams aren’t removed. The change in length makes non functional proteins

42
Q

How does nitrous acid mutate DNA

A

It changes cytosine to uracil

43
Q

What is a transition mutation

A

When a purine is changed to a purine or a pyrimidine changed to a pyrimidine

44
Q

What is a transversion mutation

A

When a purine is changed to a pyrimidine

45
Q

What cells do germ line mutations effect

A

Sperm and egg

46
Q

Why do rna errors occur often

A

RNA Polymerase don’t proofread

47
Q

Why are mutations in rna often not harmful

A

RNA degrades quickly not passed on and the cell makes multiple copies o DNA

48
Q

What organs are badly affected by mutations in mitochondria

A

Organs requiring lots of energy e.g heart, brain and muscle

49
Q

From whom do you inherit your mitochondria from

A

Your mother

50
Q

What results in aneuploidy

A

Nondisjunction

51
Q

What is anaphase lag

A

When chromosomes aren’t separated properly during anaphase

52
Q

Are are monosomy cells not usually found

A

As they are fatal and result in death

53
Q

What are primordial germ cells

A

Cells which develop into sperm and ovum

54
Q

What is the significance of large amounts of division of germ cells

A

Lots of chance for mutation

55
Q

Why does mutation rate of gametes increase with age

A

More exposure to mutagens/radiation

56
Q

What is teratogensis

A

The process by which mutations are produced in an embryo

57
Q

What do recessive mutations cause

A

Loss of function

58
Q

What do dominant mutations occur

A

Increased function

59
Q

What is cytogenetics

A

Study and analysis of chromosomes

60
Q

What constitutional Abnormalities result in referral for cytogenetic analysis

A

Prenatal diagnosis, birth defect, infertility and reoccurring fetal loss

61
Q

What acquired Abnormalities result in referral for cytogenetic analysis

A

Leukaemia, tumours and specific translocations

62
Q

What 2 types of prenatal diagnosis methods are there

A

Chorionic villus and amnioticentesis

63
Q

What is chorionic villus

A

Inserting a needle to collect some chorionic fluid which surrounds the placenta using ultrasound

64
Q

What is amniocentesis

A

Collecting amniotic fluid using a needle and ultrasound guidance

65
Q

What is polyploidy

A

Gain of a whole haploid set of chromosomes

66
Q

What causes polyploidy

A

Fertilisation of an egg by more than one sperm

67
Q

What are the causes aneuploidy

A

Nondisjunction

68
Q

What is mosicaism

A

2 cell populations in an individual

69
Q

What is Down’s syndrome

A

Trisomy 21

70
Q

What symptoms are associated with Down’s syndrome

A

Intellectual disability. Heart defects, increased incidents of leukaemia and Alzheimer’s

71
Q

What is the syndrome caused by trisomy 18

A

Edwards syndrome

72
Q

What symptoms are associated with Edwards syndrome

A

Small lower jaw, low set ears, rocker bottom feet and overlapping fingers

73
Q

What is Patau syndrome

A

Trisomy 13

74
Q

What is single X chromosome inactivation

A

Where only 1 X chromosome is ever active in a human cell

75
Q

Why is single XChromosome a problem

A

2 X chromosomes are required to activate genes

76
Q

What is the name of the syndrome when you only have 1 X chromosome

A

Turner syndrome

77
Q

What symptoms are associated with Turner syndrome

A

Puffy feet,, redundant skin at the back of the neck

78
Q

What are balanced translocations

A

Where there is an even exchange of genetic information with no loss of gain

79
Q

What are unbalanced translocations

A

Where there is a loss or gain of genetic information

80
Q

Can microarray detect both balanced and unbalanced translocations

A

No only unbalanced

81
Q

What types of segregation result in balanced translocations

A

Alternate

82
Q

What types of segregation results in unbalanced translocations

A

Adjacent, and nondisjunction

83
Q

What are Robertsonian translocations

A

When the q arms of 2 Acrocentric chromosomes fuse together

84
Q

What diagram is used to assess segregation imbalance

A

Pachytene diagram

85
Q

What are terminal deletions/duplications

A

Ones that occur towards the ends of a chromosome

86
Q

What are interstitial deletions/deletions

A

Ones that occur in the chromosome arm

87
Q

What is uniparental disomy

A

Presence of homologous chromosomes from one parent

88
Q

What is the significance of uniparental disomy

A

It affects imprinting (differential expression of genes depending on parental origin of chromosome)

89
Q

How is uniparental disomy caused

A

Trisomy rescue, mitotic error

90
Q

Why might women with balanced translocations have repeated miscarriages

A

As the separation of their chromosomes result in unbalanced translocations which aren’t viable for life

91
Q

Are gain of function mutations more likely to be dominant or recessive

A

Dominant

92
Q

What genes are mutated to give oncogenes

A

Proto oncogenes

93
Q

What is bulky adduct

A

When chemicals are added to DNA which stop it replicated

94
Q

How does nitrous acid mutate DNA

A

Changes cytosine to uracil by replacing an NH2 group

Phase 1 - S1 Medical Cell Biology And Genetics (13 decks)

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