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🧬BIOCHEM > MT1 > Flashcards

MT1 Flashcards

1
Q

what is a mis-sense mutation?

A

alters a codon so it is recognised by a different tRNA molecule

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2
Q

what is a nonsense mutation?

A

introduces premature stop codon in mRNA

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3
Q

what is satellite DNA made up of?

A

repeated sequence elements

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4
Q

what is a DNA transposon?

A

cuts sequence and pastes it elsewhere?

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5
Q

what does RNA polymerase I transcribe?

A

rRNAs (ribosomal)

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6
Q

what does RNA polymerase II transcribe?

A

mRNAs, snRNAs, snoRNAs (small nucleolar), miRNAs

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7
Q

what does RNA polymerase III transcribe?

A

tRNAs, some snRNAs (small nuclear)

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8
Q

what do general transcription factors do?

A

recognise promoter sequences and bind to them, then recruit correct RNA polymerases onto protein scaffold formed on promoter sequences

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9
Q

what is the function of peroxisomes?

A

degradation of long chain fatty acids, redox homeostasis

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10
Q

what is the function of autophagosomes?

A

deliver cellular material to lysosome, formed during nutrient starvation or damage

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11
Q

what are luminal proteins?

A

in cisternae of rough endoplasmic reticulum

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12
Q

what is the trans-golgi network?

A

network that packages proteins into carriers and directs them to their final location

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13
Q

what does a translocon do?

A

moves UNFOLDED polypeptides across a membrane

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14
Q

what SNAREs are on vesicles?

A

v-SNAREs, target membrane has 3 T-SNAREs

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15
Q

what is a ‘molecular zip code’?

A

signalling sequence used to target proteins to organelles

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16
Q

what is a membrane contact site?

A

two organelles that come into close proximity but do not fuse

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17
Q

what is the function of a membrane contact site?

A

facilitates lipid transfer between organelles

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18
Q

what are ‘stop’ codon sequences?

A

UAA, UAG, UGA

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19
Q

what is the start codon sequence?

A

AUG

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20
Q

what assembles tRNA molecules?

A

specific aminoacyl tRNA synthetases

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21
Q

what is the function of tRNA synthetases?

A

specialist enzymes that charge tRNAs with correct amino acids

22
Q

what is the ‘wobble hypothesis’?

A

base pairing rules at third base are less strict, so the base can pair with more than one complementary base

23
Q

what are the E, P and A sites?

A

E -> exit site
P -> peptidyl site
A -> aminoacyl site

24
Q

what catalyses bond formation at the A site?

A

peptidyl transferase activity

25
Q

what happens to the ribosome at the stop codon?

A

dissociates into 60S and 40S units - ribozyme (with enzymes) is catalytic part

26
Q

what direction does translation happen in?

A

3’ to 5’

N-terminus to C-terminus

27
Q

what is the role of the cap and poly(A) tail in translation?

A

cap binding proteins and poly(A) tail proteins interact, create circular mRNA molecule. this structure recruits the ribosome to the mRNA

28
Q

where is the ribosome recruited?

A

40S subunit recruited to the cap

29
Q

what are ddNTPs and what do they do?

A

di-deoxynucleotides

terminate polymerisation

30
Q

what are methods of gene expression analysis?

A

hybridisation based -> fluorescence in situ, RNAi, CRISPR

enzyme based -> PCR, next generation sequencing

antibodies -> imaging, ELISA, lateral flow, western blotting

31
Q

what is the function of the cap?

A

protects mRNA from exoribonucleases - cause degradation

initiates translation

32
Q

how does the cap bind?

A

GMP nucleotide fused to 5’ end of mRNA, G is subsequently methylated, binds protein complex (cap binding complex - CBC)

33
Q

what does kinase do in transcription?

A

phosphorylates serine 5 and serine 2 at pol II CTD

negative elongation factors release paused polymerase, allow for recruitment of spliceosome

34
Q

what mediates splicing?

A

small nuclear ribonucleic acid protein complexes (SNURPS) in spliceosome

35
Q

what is the function of cis-elements in pre-mRNA?

A

recognised by spliceosome factors, indicate where to splice

36
Q

what is alternative splicing?

A

allows permutation of exons, so multiple proteins can be generated from one gene

37
Q

how is alternative splicing regulated?

A

proteins associate with certain sequences on pre-mRNA, strengthen or weaken splice sites

38
Q

how is an exon excluded from the final mRNA?

A

negative factors bind to specific sequences, prevent recognition of 5’ and 3’ splice sites that flank exon

39
Q

what does the poly(A) tail do in transcription?

A

added at 3’ end, recruits cleavage ad polyadenylation machinery by sequence motif (AAUAAA hexamer, U-rich element)

allows cleavage and polyadenylation that matures mRNA

40
Q

what are the three groups of fibrous proteins?

A

coiled coil alpha helices
triple helix
beta sheets

41
Q

what is the structure of collagen?

A

three polypeptide chains, repeat of sequence Gly-X-Y (X = proline, Y = hydroxyproline)

42
Q

how is collagen formed?

A

one chain folds into left handed helix, helices aggregate into right handed triple helix

synthesised as procollagens with globular extensions on both ends that form disulphide bonds which align chains in register for triple helix

43
Q

what cells secrete procollagen into the extracellular space?

A

fibroblasts

44
Q

what is the structure of keratin?

A

right handed alpha helix
pair of helices twist to make a coiled coil
heptagon repeats, fibres assembled from coiled coils in staggered array

45
Q

what are ABC transporters?

A

ATP binding cassettes

responsible for excretion of xenobiotic compounds back into the gut

eg P-glycoprotein

46
Q

what is the structure of a steroid hormone receptor?

A

variable domain, DNa binding domain, hinge domain, hormone binding domain

47
Q

what are zinc fingers?

A

zinc coordinated with four cysteines
in transcription factors

motif -> 2 Cys and 2 His residues
increased motif numbers = improved specificity for DNA regions

48
Q

what is the structure of immunoglobulins?

A

amino terminal variable domain
carboxy terminal constant domain

constant domain -> seven beta strands arranged, 4 strands form one sheet, 3 form other
variable domain -> 3 small regions are variable

49
Q

how is insulin stored?

A

as a hexamer

50
Q

how is insulin released?

A

when glucose is taken into the cell via GLUT2, it is phosphorylated, decreasing glucose concentration
more glucose diffuses in -> increase in ATP conc, opening K+ channels
depolarisation occurs, opening VGCC
stimulate release of vesicles with insulin

🧬BIOCHEM (1 decks)

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