Mutations Flashcards

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1
Q

Description of gene mutation

A
  • definition: involves a (1) permanent heritable change
    (2) in one or a few bases in the nucleotide/base sequence
    (3) of one gene
  • could be the substitution of one nucleotide pair with another
  • resulting in missense / neutral / silent / nonsense mutation
  • could also be the addition or deletion of one or more nucleotide pair
  • which if not in multiples of 3, will result in a frame shift mutation
  • where all nucleotides downstream of insertion/deletion site will be improperly grouped into codons
  • resulting in extensive missense mutation
  • which if in multiples of 3, will result in missense / nonsense mutation
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2
Q

elaboration of missense mutation (in nucleotide sub)

A
  • results in a different mRNA codon
  • causing the translation of a different amino acid
  • leads to a change in aq seq
  • leads to change in 3d conformation
  • thus leads to change in protein function
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3
Q

elaboration of missense mutation (in nucleotide insertion or deletion)

A
  • results in mRNA codon being added or deleted
  • causing the polypeptide to have an amino acid added or deleted
  • leads to a change in aq seq
  • leads to change in 3d conformation
  • thus leads to change in protein function
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4
Q

elaboration of nonsense mutation (in nucleotide sub)

A
  • results in a stop codon
  • causing premature termination of translation
  • truncated protein -> non-functional
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5
Q

elaboration of silent mutation (in nucleotide sub)

A
  • results in a different mRNA codon
  • causing the translation of the same aa
  • leads to same aa seq
  • leads to same 3d conformation
  • thus no change in protein function
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6
Q

elaboration of nonsense mutation (in nucleotide insertion or deletion)

A
  • results in stop codon being added
  • causing a truncated protein
  • truncated protein -> non-functional
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7
Q

Description of chromosomal aberration (structure)

A
  • definition: change in the structure of a chromosome
  • which results in reshuffling of alleles on chromosome

Deletion:
- when chromosome breaks in one or more places,
and a portion of it lost
- missing part is referred to as a deletion

Duplication:
- when any part of the genetic material, be it a single locus or a large piece of chromosome,
is present more than once in the genome
- due to unequal crossing over between synapses chromosomes during meiosis /
through a replication error prior to meiosis

Inversion:
- when a segment of a chromosome is turned around 180º within a chromosome

Translocation:
- is the movement of a chromosomal segment to a new location in the genome

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8
Q

Description of chromosomal aberration (no.)

A
  • definition: a change in the number of chromosomes

aneuploidy:
- where there is addition or loss of one or more chromosomes

polyploidy:
- where there is addition of one or more haploid sets of chromosomes
- resulting in autopolyploidy if additional sets of chromosomes come from same species
- or resulting in allopolyploidy if additional sets of chromosomes come from different species
- due to non-disjunction / failure of chromosomes or chromatids
to disjoin and move to opp poles during division

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9
Q

How chromosomal aberration results in Down syndrome

A
  • gain of an extra chromosome 21 (X chromosome)
  • but not a complete set
  • due to non-disjunction / failure of chromosomes or chromatids to disjoin and move to opp poles
  • during anaphase I of meiosis I or anaphase II of meiosis II
  • disrupting normal distribution of chromosomes into gametes
  • forming abnormal gametes containing two members of the affected chromosome
  • fertilising these with a normal haploid gamete produces a zygote with 3 members of this chromosome
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10
Q

Symptoms of Down syndrome

A
  • characteristically short
  • stocky bodies / thick necks
  • low intelligence level
  • short life expectancy
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11
Q

elaboration on how mutation may change structure and function of protein

A
  • change in 3d conformation of protein
  • change in R grp interactions (HI or hydrogen bonds)
  • change in the binding/interaction of protein with other molecules
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12
Q

differences between GOF mutation and LOF mutation

A
  • no of mutations (needed for effect on phenotype)
    • GOF: single mutation
    • LOF: 2 mutations
  • type of allele
    • GOF: dominant allele
    • LOF: recessive allele
  • effect
    • GOF: activates/stimulates process
    • LOF: inactivates process
  • example
    • GOF: oncogene
    • LOF: tumour suppressor gene
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13
Q

differences between chromosomal and gene mutations

A
  • extent
    • chromosomal: may involve transfer of whole genes
    • gene: change in base
  • effect
    • chromosomal: changes regulation / control of expression of gene
    • gene: changes protein produced
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14
Q

when does mutations have no effect on activity of enzyme

A
  • silent mutations which result in no change in aa seq
    OR neutral mutation where change in aa is to another with similar properties
  • mutations that could result in a change in aa in a region away from binding site of enzyme
  • thus does not affect conformation / binding properties of binding site
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