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

Ch 15 The Genetic Code & Translation Flashcards

(56 cards)

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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

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A

three potential reading frames

24
Q

first mRNA codon to specify an amino acid

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A

initiation/start codon

25
what is the start codon and what does it encode in prokaryotes and eukaryotes?
AUG prokaryotes: n-formyl methionine eukaryotes: methionine
26
list the three stop/nonsense codons
UAA, UAG, UGA
27
do stop codons encode amino acids?
no, stop codons do NOT encode amino acids
28
what is meant by the genetic code is universal?
all forms of life mostly use the same genetic code
29
what are the four steps of protein synthesis (translation)
tRNA charging initiation elongation termination
30
tRNA attaches to its appropriate amino acid
tRNA charging
31
what is required for tRNA charging?
energy (ATP)
32
how do amino acids attach to tRNA?
adenine nucleotide of CCA at 3' end of tRNA binds to carboxyl group of amino acids
33
specificity of amino acids to tRNA is performed by
aminoacyl-tRNA synthetase
34
how do aminoacyl-tRNA synthetase recognize its appropriate amino acid and tRNA
amino acid: based on sizes, charges, R groups tRNA: based on tRNA nucleotide sequence
35
describe the process of tRNA charging of translation
- 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
what are the functional units of the ribosome
large subunit and small subunit
37
what is the only way mRNA can bind to subunits of ribosome
if they are separate
38
describe the process of initiation of translation in prokaryotes
- 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
describe initiation of translation in eukaryotes
- 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
describe the process of elongation of translation in prokaryotes
- 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
3 sites of ribosome
Peptidyl (P) site Aminoacyl (A) site Exit (E) site
42
what characteristic of rRNA allows P site of amino acid to be released from its tRNA?
catalytic activity (rRNA is a ribozyme)
43
what's the difference between elongation of translation in eukaryotes and prokaryotes
prokaryotesto have three elongation factors: EF-Tu, EF-Ts, EF-G eukaryotes have at least three elongation factors
44
describe the process of termination of translation in prokaryotes
- 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
what's the difference between termination of translation in eukaryotes and prokaryotes
prokaryotes have 3 release factors eukaryotes have 2 release factors: - eRF-1 recognizes all termination codons - eRF-2 binds to GDP
46
mRNA with multiple ribosomes attached
polyribosomes
47
what's the purpose of polyribosomes
allows mRNA to translate multiple proteins simultaneously
48
what are some post-translational modifications
- molecular chaperones fold polypeptide chains into their correct shapes - cleavage and trimming - removal of signal sequence - addition of chemical groups
49
enhances dissociation of large and small subunits of ribosome
initiation factor 1 (IF-1)
50
binds GTP and delivers fMet-tRNA to initiation codon
initiation factor 2 (IF-2)
51
binds to 30S small ribosomal subunit and prevents association with large ribosomal subunit
initiation factor 3 (IF-3)
52
binds GTP and charged tRNA and delivers it to A site
elongation factor Tu (EF-Tu)
53
regenerates active EF-Tu-GDP
elongation factor Ts (EF-Ts)
54
stimulates translocation of ribosome to next codon
elongation factor G (EF-G)
55
bind to stop codons
release factor 1 (RF-1) release factor 2 (RF-2)
56
binds with GTP and binds to ribosome to terminate translation
release factor 3 (RF-3)

Genetics - BIO 2306 (20 decks)

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