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FunMed Genetics > The causes of genetic mutatoins > Flashcards

The causes of genetic mutatoins Flashcards

1
Q

what is a mutation

A

this is a sudden change in genetic trait - it changes the DNA code

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2
Q

the change is….

A

then heritable – somatic mutation is passed on to daughter cells and if its in a germ mutation is passed onto the next generation

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3
Q

can mutations be good or bad

A

Both

  • positive is that they drive evolutionary change
  • the negative is that they cause many diseases
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4
Q

what are the types of mutations that you need to know about

A
  • point mutations
  • frameshift mutations
  • chromosomal mutations
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5
Q

mRNA codon that you need to know about

A
  • AUG = this is methionine and is a start codon
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6
Q

describe point mutations

A
  • Changes in a single base pair in DNA – these do not interfer much with protein function but can be bad
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7
Q

what are the three types of point mutations

A
  • Silent
  • Missense
  • Nonsense
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8
Q

describe silent

A
  • Three base codon changes but the same amino acid is coded
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9
Q

describe missense

A
  • Conserved – changes the amino acid coded but one that has similar properties
  • Non-conservative – changes amino acid coded to one that has different properties
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10
Q

describe non sense

A
  • Leads to premature stopping of the amino acid sequence
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11
Q

what are the two types of missense mutations

A

conserved and non conservative

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12
Q

describe examples of point mutations

A

sickle cell anaemia

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13
Q

describe sickle cell anaemia

A
  • Mutation in a single nucleotide
  • Causes change in amino acid from glutamic acid to valine – non conservative missense
  • Glutamic acid is a charged amino acid whereas valine is hydrophobic
  • Changes in the properties of haemoglobin molecules that carries oxygen to the cells
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14
Q

what are the frameshift mutations

A
  • Where a single base is added or deleted from the DNA
  • Adding or deleting 1 base changes every amino acid in the protein after this point
  • Proteins don’t function properly
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15
Q

what is an example of frameshift

A
  • tay-sacks disease
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16
Q

describe tay-sachs disease

A
  • Mutations in beta-hexosaminidase A (Hex-A)
  • Most are point mutations (65/78)
  • 8 frameshift mutations – 6 deletions and 2 insertions,
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17
Q

what are deletions

A

part of chromosome is left out

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18
Q

what are duplications

A

part of a chromosome breaks off and attaches to the sister chromatid

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19
Q

what are inversions

A

part of a chromosome breaks off and reinserts backwards these don’t usually cause any problems as long as its balanced

20
Q

what are translocations

A

– part of a chromosome breaks off and attaches to a different chromosome
- changes gene location on chromosome and can change a number of copies of a gene

21
Q

what are examples of deletions

A

cri du chat

di George syndrome

22
Q

what are examples of duplications

A

Charcot marie tooth disease

23
Q

what are examples of translocation

A

XX* male syndrome

24
Q

describe cri du chat

A
  • Partial deletion of the short arm of chromosome 5

- 90% are sporadic and de novo deletions

25
Q

describe di George syndrome

A
  • Deletion of a region of a long arm chromosome 22
  • Microdeletion
  • Majority of cases are de novo
26
Q

describe Charcot marie tooth disease

A
  • Most common heritable peripheral neuropathy
  • 70-80% of cases duplication of large region of short arm of chromosome 17
  • Includes gene peripheral myelin protein 22
27
Q

describe XX* male syndrome

A
  • Translocation of SRY gene from Y chromosome to X chromosome
28
Q

describe nondisjunction

A
  • Chromosomes fail to separate properly
  • Leads to trisomy – extra chromosome – diseases such as down syndrome
  • Monosomy – lack of chromosome – usually not viable and frequent in misccariages
  • Triploidy – 3 sets of chromosomes – banana plants, sterile and need clonal propagation, in humans triploid babies will miscarry or die within 1st year of life
29
Q

what are spontaneous mutations

A
  • Arise from errors in replication processes and base modifications
  • Eukaryotes = rate 10-4 – 10-6 per gene per generation
  • Natural error rate for DNA polymerase
  • Many are corrected by cellular repair systems so are repaired before they are transmitted
  • Base modifications – depurination, deamination, tautomeric shift
  • Base insertion and deletion
30
Q

what are the origins of spontaneous mutations

A

can arise by 3 types of chemical changes

  • deprivation
  • deamination
  • tautomeric shift
31
Q

describe depurination

A

loss of purine base A or G

32
Q

describe deamination

A

changes a normal base to atypical base for example C to U, this can be corrected or 5-methylcyotisine to hypoxantine which is irreparable

33
Q

describe tautomeric shift

A

repositioning of hydrogen atoms that lead to mismatching, guanine will pair with thymine rather than cytosine

34
Q

what is a mutagen

A

it is an agent which causes genetic mutation

35
Q

what do mutagens do

A

they increase the number of mistakes from 1000 to 100,000 per replicated gene

36
Q

what are the types of mutagens

A
  • physical
  • chemical
  • biological
37
Q

name the physical mutagens

A
  • UV rays
  • radiation
  • extreme heat
38
Q

name the chemical mutagens

A
  • nicotine
  • pesticides
  • methane
39
Q

name the biological mutations

A
  • bacteria

- viruses

40
Q

what types of radiation is there

A
  • direct

- indirect

41
Q

describe direct radiation

A
  • When alpha particles, beta particles or x rays create ions which physically break sugar phosphate backbone, connections between base pairs or chemically alter bases
  • Bases held together by hydrogen bonds when broken
  • If two pyrimidines of the same type (T or C) are next to each other they bind to each other distoriting DNA
42
Q

describe indirect radiation

A
  • Creation of free radicals where the presence of unpaired electrons damages bases or breaks backbone
43
Q

what does smoking cause

A
  • 1,000,000 deaths due to lung cancer
  • Double strand breaks
  • Base pair trans-versions
44
Q

name infectious agents

A
  • Human papilloma virus – viral DNA is incorporated into host and can disable normal DNA damage repair processes
  • Helicobacter pylori – infection can cause stomach cancer and can induce reaction oxygen species
45
Q

what is a codon

A

three adjacent nucleotides that Code for an amino acid

46
Q

name chromosomal mutations

A
  • non dissection
  • deletion
  • duplication
  • inversion
  • translocation

FunMed Genetics (12 decks)

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