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MCB 150 > Mutations + Cytoskeleton > Flashcards

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
Q

Chromosomal level mutations

A
  • insertion/deletion
  • duplication
  • inversion
    -translocation (in relation to non homologous chromosomes)
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26
Q

Some lymphomas and leukemias caused by

A
  • translocations
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27
Q

Many oncogenes are activated and become cancers though

A
  • duplications
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28
Q

Fragile X syndrome and Huntington’s disease are also caused by

A
  • duplications of short, repeated sequences
29
Q

Infertility

A
  • if inversions dont involve the loss of DNA they are often silent, but can cause this
30
Q

Haemophilia A often caused by

A

Insertion mutations

31
Q

Ames test for mutagenicity

A
  • 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
Q

Cytoskeleton

A
  • dynamic system of protein fibers of various sizes
  • can be reorganized as needed
  • provides physical support and allows for movement.
33
Q

Actin structure, and characteristics (G) (5)

A
  • 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
Q

Components of cytoskeleton

A
  • microtubules
  • microfilaments
  • intermediate filaments
35
Q

Microtubules

A
  • an tubulin
  • 25nm outer diameter
36
Q

How to actin monomers polymérisé

A
  • in microfilaments
  • adopts a helical shape
  • prefer to add to the plus end
37
Q

What does polymérisation of actin begin with

A
  • nucleation
38
Q

Nucleation

A
  • 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
Q

Actin polymérisation

A
  • ATP bound actin ahs higher affinity for other actins
  • when actin binds to other actin, ATP hydrolyses to ADP
40
Q

Actin microfilaments assembled in 3 ways

A
  • actin bundles
  • actin networks
  • actin contractile elements
41
Q

Actin bundles

A
  • can form microvilli (actin bundles stabilise this extension of the cytoplasm) which increase surface area by 10-20x time
42
Q

Actin networks

A
  • provides structural stability but are more flexible than bundles
  • actin binding protein link filaments together.
  • eg terminal web under the plasma membrane
43
Q

Myosin

A

Converts chemical energy to mechanical energy (kinetic) which generates force and movement

44
Q

Actin and myosin responsibilities examples

A
  • cell division
  • cell crawling
  • some vesicle movement
  • muscle contraction
45
Q

What cancels do with a combination of actin and myosin

A
  • cytokinesis - contractile ring of actin with myosin fibers
  • cell crawling
  • vesicle movement
46
Q

Level of organisation of muscle fiber

A
  • tissue - bundle of muscle fibers - muscle fiber - myofibrils- sarcomere
47
Q

I band

A
  • area of only actin
48
Q

Z line

A

2 Z lines = sacromere

49
Q

H zone

A
  • myosin area only
50
Q

A band

A
  • area of overlap of myosin and actin fibers
51
Q

M line

A
  • middle of sarcomere
52
Q

Microtubules

A
  • guides intracellular transport
  • segregating chromosomes during mitosis
  • propulsion or sweeping of fluids over membranes
53
Q

Microtubule material

A
  • tubulin
54
Q

A tubulin

A
  • had GTP binding site
55
Q

B tubulin

A
  • has GTP binding site, but gets hydrolyzed to GDP during polymerisation
56
Q

Tubulin polymerization

A
  • 13 linear protofilaments surrounding a hollow core
  • assembled head-to-tail so Microtubule has polarity
57
Q

Microtubule behavior influence by drugs

A
  • binding tubulin
  • binding Microtubule
58
Q

Binding tubulin drugs

A
  • induces polymerisation at 2 things: Nonspecifically affects all MTs, and Targets rapidly dividing cells
  • (Non specific) : Colchicine and Colcemid
  • (Rapdily dividing cells: vincristine)
59
Q

Binding Microtubule drugs

A
  • stabilises Microtubules
  • targets rapidly dividing cells
  • eg taxol
60
Q

IN vivo, what happens to tubulin dimers

A
  • most polymerisation and dépolarisation happens at plus end.
  • because minus end has something on it
61
Q

Where do new microtubules come from

A
  • Microtubules organizing centres (MTOC)
  • primary MTOC is centrosome in animal cells
62
Q

Centrioles

A

9 triplet arrangements of microtubules of A.B,C microtubules

63
Q

Pericentriolar material

A
  • Amorphous collection of protein from which MTs emanate
  • gamma tubulin present for efficient Microtubule formation in the PCM.
64
Q

True or false; MTs originate in the centrosome but stay there

A

False - stable microtubules can be removed and placed into other parts of the cell.

65
Q

Microtubules motor protein

A

Kinesin - move toward the plus end
Dyneins - move toward the minus end of the Microtubule

66
Q

Functions of microtubules and associated motor proteins

A
  • Intracellular vesicle transport
    • Organelle movement and positioning
    • Color changes
    • Bending of cilia and flagella
    • Separation of sister chromatids and centrosomes during
    M-phase
67
Q

Axoneme

A
  • 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
Q

Basal body

A
  • minus end of axonene MTs anchored in a basal body
69
Q

Duchenne’s muscular dystrophy caused by

A

A deletion mutation

MCB 150 (8 decks)

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