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Genetics - BIO 2306 > Ch 15 The Genetic Code & Translation > Flashcards

Ch 15 The Genetic Code & Translation Flashcards

1
Q

structure of amino acid

A

central carbon atom bonded to amino group, hydrogen atom, carboxyl group, and R group

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2
Q

what links amino acids

A

peptide bonds

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3
Q

free amino group

A

amino end (N-terminus)

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4
Q

free carboxyl end

A

carboxyl end (C-terminus)

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5
Q

how many common amino acids are there?

A

20 common amino acids

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6
Q

through what process is a peptide bond formed to link amino acids

A

dehydration synthesis (production of water molecule)

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7
Q

protein structure: sequence of amino acids

A

primary structure

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8
Q

protein structure: interactions between amino acids

A

secondary structure

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9
Q

common secondary structures

A

alpha helix, beta pleated sheets

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10
Q

protein structure: folding of secondary structures (R group interactions)

A

tertiary structure

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11
Q

protein structure: 2 or more polypeptide chains association

A

quaternary structure

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12
Q

group of amino acids forming a discrete functional unit in a protein

A

domain

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13
Q

set of three nucleotides that encode a single amino acid

A

codon

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14
Q

how many possible codons are there?

A

(4 possible bases): 4^3 = 64 possible codons

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15
Q

codons that encode amino acids

A

sense codons

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16
Q

codons that specify end of translation

A

nonsense/stop codons

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17
Q

explain degeneracy of genetic code

A

amino acids may be specified by more than one codon

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18
Q

codons that specify the same amino acid

A

synonymous codons

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19
Q

tRNAs that have different anticodons but accept the same amino acids

A

isoaccepting tRNAs

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20
Q

nonstandard base pairing at 3rd position (3’) of codon due to it pairing weakly and allowing flexibility

A

wobble

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21
Q

explain how one anticodon can pair with more than one codon

A

pairing at the third codon is weak (wobble)
more than one base can pair with that 3rd position

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22
Q

how is the genetic code considered nonoverlapping

A

each nucleotide is part of a single codon

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23
Q

how many potential reading frames are there for any sequence of nucleotides

A

three potential reading frames

24
Q

first mRNA codon to specify an amino acid

A

initiation/start codon

25
Q

what is the start codon and what does it encode in prokaryotes and eukaryotes?

A

AUG
prokaryotes: n-formyl methionine
eukaryotes: methionine

26
Q

list the three stop/nonsense codons

A

UAA, UAG, UGA

27
Q

do stop codons encode amino acids?

A

no, stop codons do NOT encode amino acids

28
Q

what is meant by the genetic code is universal?

A

all forms of life mostly use the same genetic code

29
Q

what are the four steps of protein synthesis (translation)

A

tRNA charging
initiation
elongation
termination

30
Q

tRNA attaches to its appropriate amino acid

A

tRNA charging

31
Q

what is required for tRNA charging?

A

energy (ATP)

32
Q

how do amino acids attach to tRNA?

A

adenine nucleotide of CCA at 3’ end of tRNA binds to carboxyl group of amino acids

33
Q

specificity of amino acids to tRNA is performed by

A

aminoacyl-tRNA synthetase

34
Q

how do aminoacyl-tRNA synthetase recognize its appropriate amino acid and tRNA

A

amino acid: based on sizes, charges, R groups
tRNA: based on tRNA nucleotide sequence

35
Q

describe the process of tRNA charging of translation

A
  • amino acid reacts with ATP to produce aminoacyl-AMP
  • amino acid is transferred to corresponding tRNA, where carboxyl group of amino acid attaches to A of CCA of tRNA
  • AMP is released
36
Q

what are the functional units of the ribosome

A

large subunit and small subunit

37
Q

what is the only way mRNA can bind to subunits of ribosome

A

if they are separate

38
Q

describe the process of initiation of translation in prokaryotes

A
  • IF3 binds to small subunit, allowing small subunit to bind to Shine-Dalgarno sequence within mRNA
  • t-RNA charged with fMET forms a complex with IF-2 and GTP, and binds to initiation/start codon
  • IF-1 joins to the small subunit, causing all initiation factors to dissociate from the complex and GTP –> GDP
  • large subunit joins to create 70S initiation complex
39
Q

describe initiation of translation in eukaryotes

A
  • initiation complex recognizes 5’ cap and binds ribosome there
  • ribosome moves –> 3’ until AUG is reached
  • proteins in 3’ poly(A) tail interact with cap-binding proteins, forming a loop and enhances the binding of ribosome to 5’end
40
Q

describe the process of elongation of translation in prokaryotes

A
  • fMET tRNA occupies P site of ribosome
  • EF-Tu forms complex with GTP and charged tRNA and placed in A site of ribosome
  • GTP –> GDP, and EF-Tu GDP complex is released
  • EF-Ts regenerates EF-Tu-GDP into EF-Tu-GTP, which is ready to combine with another charged tRNA
  • peptide bond forms between amino acids in P and A site and tRNA in the P site releases its amino acid
  • EF-G and hydrolysis of GTP –> GDP allows translocation of ribosome down mRNA
  • tRNA in P site moved to E site and exits into cytoplasm; tRNA in A site moved to P site and A site is open for another tRNA
41
Q

3 sites of ribosome

A

Peptidyl (P) site
Aminoacyl (A) site
Exit (E) site

42
Q

what characteristic of rRNA allows P site of amino acid to be released from its tRNA?

A

catalytic activity (rRNA is a ribozyme)

43
Q

what’s the difference between elongation of translation in eukaryotes and prokaryotes

A

prokaryotesto have three elongation factors: EF-Tu, EF-Ts, EF-G
eukaryotes have at least three elongation factors

44
Q

describe the process of termination of translation in prokaryotes

A
  • ribosome translocates to a stop codon –> no tRNA pairs
  • RF-1 or RF-2 bind to A site where the stop codon is
  • RF-3 forms complex with GTP and binds to ribosome
  • polypeptide is released from tRNA in the P site
  • GTP with RF3 hydrolyzed to GDP
  • tRNA, mRNA, and release factors are released from the ribosome
45
Q

what’s the difference between termination of translation in eukaryotes and prokaryotes

A

prokaryotes have 3 release factors
eukaryotes have 2 release factors:
- eRF-1 recognizes all termination codons
- eRF-2 binds to GDP

46
Q

mRNA with multiple ribosomes attached

A

polyribosomes

47
Q

what’s the purpose of polyribosomes

A

allows mRNA to translate multiple proteins simultaneously

48
Q

what are some post-translational modifications

A
  • molecular chaperones fold polypeptide chains into their correct shapes
  • cleavage and trimming
  • removal of signal sequence
  • addition of chemical groups
49
Q

enhances dissociation of large and small subunits of ribosome

A

initiation factor 1 (IF-1)

50
Q

binds GTP and delivers fMet-tRNA to initiation codon

A

initiation factor 2 (IF-2)

51
Q

binds to 30S small ribosomal subunit and prevents association with large ribosomal subunit

A

initiation factor 3 (IF-3)

52
Q

binds GTP and charged tRNA and delivers it to A site

A

elongation factor Tu (EF-Tu)

53
Q

regenerates active EF-Tu-GDP

A

elongation factor Ts (EF-Ts)

54
Q

stimulates translocation of ribosome to next codon

A

elongation factor G (EF-G)

55
Q

bind to stop codons

A

release factor 1 (RF-1)
release factor 2 (RF-2)

56
Q

binds with GTP and binds to ribosome to terminate translation

A

release factor 3 (RF-3)

Genetics - BIO 2306 (20 decks)

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