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MCAT - Bio/BC > genetic code (1B) > Flashcards

genetic code (1B) Flashcards

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1
Q

order of the central dogma

A

DNA –> transCRIPtion –> RNA –> tranSLAtion –> protein

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2
Q

where is DNA found?

A

nucleus

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3
Q

where does transcription happen

A

nucleus

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4
Q

where does translation happen

A

cytoplasm

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5
Q

what organelle makes proteins

A

ribosomes

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6
Q

mRNA is a sequence of

A

nucleotides

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7
Q

3 nucleotides (aka a codon) code for an

A

Amino acid (AA)

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8
Q

where is the anticodon located

A

on the tip of the tRNA

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9
Q

why are genetic codes considered degenerate

A

bc more than one codon codes for a given Amino Acid

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10
Q

what is the wobble position

A

the third base in the codon

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11
Q

what happens when there’s a mutation in the wobble position

A

there’s no effect on the expression of the AA –> so no adverse effect on the polypeptide sequence

wobble = designed to protect against mutations

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12
Q

missense codon

A

mutated codon that results ina DIFFERENT AMINO ACID

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13
Q

nonsense codon

A

mutated codon that results in a STOP codon

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14
Q

what is the initiation codon and what does it signal ?

A

AUG

the start of translation

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15
Q

what are the termination codons and what do they signal ?

A

UGA, UAG, UAA

the end of translation

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16
Q

what is unique to termination codons and not others

A

tRNA is not involved

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17
Q

what terminates translation

A

a protein called release factor

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18
Q

what protects the 5’ end of mRNA from exonuclease degradation

A

5’ cap (a modified nucleotide) that’s linked in a special way to mRNA

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19
Q

what protects the 3’ end of mRNA from exonuclease degradation

A

poly-A tail

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20
Q

difference between eukaryotic and prokaryotic mRNA

A

eukaryotic have 5’ cap - nucleotides - 3’ poly A tail while prokaryotic mRNA don’t have the cap nor the tail

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21
Q

what type of RNA are products of transcription: transfer RNA (tRNA), ribosomal RNA (rRNA) and/or messenger RNA (mRNA)?

A

all 3: tRNA, mRNA, rRNA

22
Q

what type of RNA are templates for translation: transfer RNA (tRNA), ribosomal RNA (rRNA) and/or messenger RNA (mRNA)?

A

mRNA

23
Q

role of tRNA?

A

responsible for bringing in the right AA for translation

24
Q

role of rRNA?

A

make up ribosomes which are responsible for translation (ribosomes turn mRNA into protein)

25
Q

what is the tRNA structure? i.e. what’s at the tip and the tail

A

at the tip is an anticodon and at the tail is an amino acid

26
Q

at the 3’ end of the tRNA, the amino acid is attached to what? via what?

A

attached to 3’OH (tertiary alcohol? look into) via ester linkage

27
Q

rRNA has an active site for

A

catalysis

28
Q

the rRNA of large ribosomal subunit is responsible for

A

catalyzing peptide bond formation & can do this even without ribosomal proteins

29
Q

first step of transcription is: chain INITIATION which involves…

A

RNA polymerase binds to promoter (TATA box) of (closed) double stranded DNA –> causing double stranded DNA complex to open

30
Q

second step of transcription is: chain ELONGATION which involves…

A

nucleoside triphosphates (A,U,G,C) adds the corresponding to the DNA template

31
Q

are primers required for transcription

A

no

32
Q

RNA is made in what direction

A

5’ to 3’

33
Q

third step of transcription is: chain TERMINATION which can happen in 2 ways - describe them

A

(1) intrinsic termination - specific sequences (termination sites) create a stem loop structure on RNA that causes RNA to slip off the template
(2) rho dependent termination - the rho factor (a protein) bumps off the polymerase

34
Q

RNA molc capable of catalyzing specific chemical reactions

A

ribozyme

35
Q

small nuclear RNAs (snRNA)

A

complex with proteins to form small nuclear ribonuclearproteins (snRNPs) to splice primary RNA transcripts

36
Q

small nuclear ribonuclearproteins (snRNPs) combined with unmodified pre-mRNA to form a

A

spliceosome = large complex where splicing of pre-mRNA occurs

37
Q

what would happen if there were less introns or alternative splicing

A

less protein variability

38
Q

what are used to splice introns

A

snRNAs / snRNP

39
Q

what are the post-transcriptional modifications (3)

A

adding of the 5’cap, poly A tail and splicing

40
Q

t/f: adding of the cap and polyA tail is considered post-transcriptional

A

true

41
Q

what enzyme catalyzes protein synthesis

A

ribosome

42
Q

which ribosome subunit is responsible for recognizing mRNA and binds to Shine-dalgarno sequence on mRNA in prokaryotes (kozak seq in eukaruotes)

A

small

43
Q

first step of translation is: chain INITIATION which involves…

A

combining mRNA, initiator tRNA, and ribosome

this complex forms around initiation codon (AUG)

44
Q

second step of translationg is: chain ELONGATION which involves…

A

(1) binding
(2) peptidyl transfer
(3) translocation

45
Q

protein is made from what terminus to what

A

N terminus to C

46
Q

mRNA reads in what direction

A

5’ to 3’ end

47
Q

during the binding portion of chain elongation, new tRNA and its amino acid (aminoacyl-tRNA) enters the A site.
what is required for this to happen

A

GTP and elongation factor

48
Q

during the peptidyl transfer portion of chain elongation, attachment of the new AA to existing chain in the P site. This chain in the P site migrates and attaches to…

A

the aminoacyl-tRNA in the A site

49
Q

the codon that was in the A site goes where after translocation (part 3 of translation elongation)

A

its now in the P site

**watch video on this…v confusing

50
Q

second step of translation is: chain termintion which involves…

A

stop codon encountered –> release factor proteins bound to GTP block the A site –> peptide chain gets cleaved from tRNA –> peptide chain falls off and whole translation complex falls apart

51
Q

inactivation by tagging protein for proteasome degradation

A

ubiquitination

52
Q

list 3 examples of post-translational modifications to proteins

A

phosphorylation
glycosylation
ubiquitination

MCAT - Bio/BC (3 decks)

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