Mutations + Cytoskeleton Flashcards

1
Q

Mutations

A
  • heritable changes in DNA
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2
Q

In single cell organisms, will all daughter cells have a mutation

A

Yes

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3
Q

Somatic mutation

A

Mutation in a non-gamete
Passed to daughter cells in area

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4
Q

Germ-line mutation

A
  • mutation in sex cells
  • passed onto new organisms - onto offspring
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5
Q

Why are mistakes in transcription or translation not as critical

A

Many copies of RNA produced
RNA are not heritable over multiple generations

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6
Q

What can cause mutations

A
  • High intensity radiation
  • chemical mutagens
  • uncorrected mistakes in replication
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7
Q

Proofreading in DNA

A

3’ to 5’ exonuclease activity in DNA polymerase (as in, it acts in the 3’ to 5’ direction) so it can backtrack.

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8
Q

Mis Match repair system

A
  • in E. coli, it scans recently synthesized DNA looking for mismatches and hemimethylated DNA )Methyl group added to an A in a GATC sequence in te replicated strand
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9
Q

2 broad categories of mutation

A

Point
Chromosomal level

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10
Q

Point mutations

A
  • base substitution
  • frameshift mutation
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11
Q

Chromosomal level

A
  • insertion/deletion
  • inversion
  • duplication
  • translocation
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12
Q

Transition

A
  • when a purine is changed with a purine, and a pyrimidine with a pyrimidine etc
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13
Q

Transversion

A
  • when a purine is replaced with a pyrimidine and vice versa
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14
Q

Missense mutation

A
  • when in a coding region of DNA, the codon changes in one base an changes the amino acid that is coded for.
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15
Q

Nonsense mutation

A
  • when one base in a codon is changed to a stop codon in a coding region of DNA
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16
Q

Same sense mutation

A

When a base in a codon is changed, but still codes for the same amino acid. (Will not notice mutation)

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17
Q

Consequence of same sense mutations

A
  • nucleotide changed to a different codon that specifies the same amino acid
  • due to redundancy of codons
  • no effect on protein/function
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18
Q

Nonsense mutation consequence

A
  • codon changes to a stop codon causing termination prematurely
  • almost always causes an inactive protein
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19
Q

Missense mutation consequences (incomplete)

A
  • codon change to codon specifying another amino acid.
  • if the amino acid wasn’t that important, or changes to a similar amino acid (with similar properties) then it will be at least partially functional.
  • but if important, then protein will likely be inactive.
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20
Q

Sickle cell Anemia mutation characteristics

A
  • Glu to Val (number 6)
  • caused by defective b globin subunit in hemoglobin protein
  • single base pair sub changes charge of protein
  • this causes hemoglobin protein to fold incorrectly
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21
Q

Possible changes of codons

A
  • same box - when you change 3rd base
  • same column (horizontally) - when you change 2nd base
  • same row (vertically) relative position - when you change 1st base
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22
Q

Truncation

A
  • premature appearance of stop codon
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23
Q

Effect of an in frame removal of 3 bases

A
  • one amino acid would be removed, rest of protein unaffected
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24
Q

CF cause

A
  • in frame deletion of PhenylAlanine codon at AA 508 of a 1400 AA protein
  • Cl- accumulates in cells, causing thick mucus (due to water moving out of mucus)
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25
Chromosomal level mutations
- insertion/deletion - duplication - inversion -translocation (in relation to non homologous chromosomes)
26
Some lymphomas and leukemias caused by
- translocations
27
Many oncogenes are activated and become cancers though
- duplications
28
Fragile X syndrome and Huntington’s disease are also caused by
- duplications of short, repeated sequences
29
Infertility
- if inversions dont involve the loss of DNA they are often silent, but can cause this
30
Haemophilia A often caused by
Insertion mutations
31
Ames test for mutagenicity
- take mutated strain of bacteria that can’t grow without presence of histidine in one test tube, and in the other, add the suspected mutagen - grow on plates without histidine - incubate to allow growth - might grow a colony or 2 - suggests that spontaneous mutations are the cause - a large number of colonies in the one with suspected mutagen suggests that suspected mutagen is the thing that actually caused mutation.
32
Cytoskeleton
- dynamic system of protein fibers of various sizes - can be reorganized as needed - provides physical support and allows for movement.
33
Actin structure, and characteristics (G) (5)
- 43kDa protein made of 375 amino acids - has nucleotide binding site that can accommodate ATP or ADP - Has polarity directionally (Pointed or barbed) - highly conserved protein - very abundant
34
Components of cytoskeleton
- microtubules - microfilaments - intermediate filaments
35
Microtubules
- an tubulin - 25nm outer diameter
36
How to actin monomers polymérisé
- in microfilaments - adopts a helical shape - prefer to add to the plus end
37
What does polymérisation of actin begin with
- nucleation
38
Nucleation
- G actin molecules randomly bump into each other - actin binding molecules facilitate this - forms dimers and trimmers - nucleation is RDS - non covalent, but stable interactions - can add both ends and depolymerize at both ends, but favored at the plus end (adding) and dépolymérisation favored at the minus end.
39
Actin polymérisation
- ATP bound actin ahs higher affinity for other actins - when actin binds to other actin, ATP hydrolyses to ADP
40
Actin microfilaments assembled in 3 ways
- actin bundles - actin networks - actin contractile elements
41
Actin bundles
- can form microvilli (actin bundles stabilise this extension of the cytoplasm) which increase surface area by 10-20x time
42
Actin networks
- provides structural stability but are more flexible than bundles - actin binding protein link filaments together. - eg terminal web under the plasma membrane
43
Myosin
Converts chemical energy to mechanical energy (kinetic) which generates force and movement
44
Actin and myosin responsibilities examples
- cell division - cell crawling - some vesicle movement - muscle contraction
45
What cancels do with a combination of actin and myosin
- cytokinesis - contractile ring of actin with myosin fibers - cell crawling - vesicle movement
46
Level of organisation of muscle fiber
- tissue - bundle of muscle fibers - muscle fiber - myofibrils- sarcomere
47
I band
- area of only actin
48
Z line
2 Z lines = sacromere
49
H zone
- myosin area only
50
A band
- area of overlap of myosin and actin fibers
51
M line
- middle of sarcomere
52
Microtubules
- guides intracellular transport - segregating chromosomes during mitosis - propulsion or sweeping of fluids over membranes
53
Microtubule material
- tubulin
54
A tubulin
- had GTP binding site
55
B tubulin
- has GTP binding site, but gets hydrolyzed to GDP during polymerisation
56
Tubulin polymerization
- 13 linear protofilaments surrounding a hollow core - assembled head-to-tail so Microtubule has polarity
57
Microtubule behavior influence by drugs
- binding tubulin - binding Microtubule
58
Binding tubulin drugs
- induces polymerisation at 2 things: Nonspecifically affects all MTs, and Targets rapidly dividing cells - (Non specific) : Colchicine and Colcemid - (Rapdily dividing cells: vincristine)
59
Binding Microtubule drugs
- stabilises Microtubules - targets rapidly dividing cells - eg taxol
60
IN vivo, what happens to tubulin dimers
- most polymerisation and dépolarisation happens at plus end. - because minus end has something on it
61
Where do new microtubules come from
- Microtubules organizing centres (MTOC) - primary MTOC is centrosome in animal cells
62
Centrioles
9 triplet arrangements of microtubules of A.B,C microtubules
63
Pericentriolar material
- Amorphous collection of protein from which MTs emanate - gamma tubulin present for efficient Microtubule formation in the PCM.
64
True or false; MTs originate in the centrosome but stay there
False - stable microtubules can be removed and placed into other parts of the cell.
65
Microtubules motor protein
Kinesin - move toward the plus end Dyneins - move toward the minus end of the Microtubule
66
Functions of microtubules and associated motor proteins
- Intracellular vesicle transport • Organelle movement and positioning • Color changes • Bending of cilia and flagella • Separation of sister chromatids and centrosomes during M-phase
67
Axoneme
- 9+2 arrangement (9 doublets + an extra pair) - unit of function in cilia or flagellum - central pair is NON connected and complete 13 protofilaments (the extra pair) - radial spoke proteins - nexin links connect outer doublet microtubules
68
Basal body
- minus end of axonene MTs anchored in a basal body
69
Duchenne’s muscular dystrophy caused by
A deletion mutation