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Genetics > Translation > Flashcards

Translation Flashcards

0
Q

______ three nucleotide codons in mRNA encode 20 amino acids + start and stop codons; most amino acids have multiple codons; codons are read in the _____ direction with the ___ terminal nucleotide at the left

A

64 codons; 5’ to 3’, 5’ at left

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1
Q

The conversion of information in RNA to protein = ______

A

Translation (of one language to another)

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2
Q

one codon– _____ – acts as both initiation signal and methionine

A

AUG

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3
Q

There are three possible reading frames in protein synthesis; RNA can be translated 3 different ways. What can go wrong..?

A

(one base pair mutation), single deletion, single addition= shifted reading frame

*as long as non multiple of 3

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4
Q

______ match amino acids to codons in mRNA

A

tRNA

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5
Q

tRNA recognizes 5’ codon on mRNA and binds/recognizes a specific _______ at the 3’

A

amino acid

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6
Q

The Anticodon of tRNA is :

A

set of 3 consecutive nucleotides that pairs with the complementary codon on the mRNA

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7
Q

the short, single stranded region on the 3’ end of tRNA….

A

recognizes and binds a SPECIFIC amino acid that corresponds to the condon

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8
Q

Some tRNAs only require accurate base-pairing only …..position of the codon and can tolerate a mismatch (WOBBLE) at the _____ position

A

first two positions must be accurate, third can wobble

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9
Q

Wobble base-pairing explains….

A

why so many alternative codons for AA differ only in their third nucleotide

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10
Q

Recognition and attachment of the correct AA to a tRNA depends on enzymes called _________ which:

A

amionacyl-tRNA synthetases: covalently couple AA to appropriate tRNA

**one for each AA (20)

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11
Q

Synthetases use ______ to produce a high-energy bond between the ____ end of the tRNA and an amino acid. The energy of this bond is used at a later step to link…

A

ATP hydrolysis ; 3’ end

NRG used to link AA covalently to growing peptide chain

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12
Q

Amino acids are added to the ____-terminal end of a growing polypeptide chain

A

C-terminal

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13
Q

Fundamental Reaction of Translation:

A

Formation of peptide bond between Carboxyl-group (o-c=o) at the end of the growing polypeptide chain and the free amino group (NH2) on the incoming amino acid

**nucleophilic attack

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14
Q

A protein is synthesized from its _____ end to its ______ end

A

N to C

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15
Q

Each amino acid carries within it the activation energy for the addition of the next amino acid from the breaking of the….

A

covalent linkage between the tRNA and the carboxyl end of the polypeptide chain

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16
Q

The formation of each peptide bond is energetically favorable because…

A

the growing C-terminus has been activated by the covalent attachment of the tRNA molecule

17
Q

The ______ subunit of ribosomes recognizes mRNA and only once correctly position, the ____ subunit is added

A

Small recognizes, then large is added

18
Q

Ribosomes are made of:

A

proteins (1/3) ++++ RNA molecules (rRNA) (2/3)

19
Q

The small subunit of ribosomes:

A

matches tRNA to the codon of the mRNA

20
Q

The large subunit of ribosomes:

A

catalyzes formation of peptide bonds

21
Q

_______ form the E, P, and A tRNA binding sites

A

rRNA

22
Q 
Prokaryotic Ribosome (70S)
Large subunit (50s) ------ Small subunit (30S)
5S+23S+ proteins= 50S
16S+ proteins=30S
A

Look at a picture

23
Q

Eukaryotic Ribosome= 80S
Large subunit=60S ——- Small subunit= 40S
5S+28S+5.8S+ proteins= 60S
18S+ proteins= 40S

A

Look at picture

24
Q

Three tRNA binding site:
A=
P=
E=

A 
A= incoming aminoacyl-tRNA ===tRNA + amino acid
P= existing peptidyl-tRNA bond
E= exiting of tRNA
25
Q

Translation begins with the ____ codon, thus all new proteins have ______ at their _____ terminal (which is usually removed)

A

AUG–> Methionine which is at N terminus

26
Q

(eukaryotes) the initiator tRNA is first loaded onto the small subunit with proteins called ______

A

eukaryotic initiation factors (eiFs)

27
Q

After tRNAi binds with eiFs, the small subunit binds the 5’ end of mRNA which is recognized by….and it then proceeds to look for first AUG (assisted by helicases)

A

the 5’ cap and eiFs

28
Q

After the small subunit finds AUG start site…..

A

eiFs dissociate, allowing for large subunit to join

**tRNAi now occupies P site, A site awaits next aminoacyl-tRNA

29
Q

The start codon selection in bacteria is different since bacterial mRNA don’t have a 5’ cap, instead they….

A

have a specific sequence called the Shine-Delgarno sequence

30
Q

bacterial mRNAS are ________ whereas eukaryotic mRNAS generally only encode for a single protein

A

polycistronic

31
Q

Three major steps of Elongation:
1)
2)
3)

A

1) new tRNA binds to A site (codon base pairing)
2) carboxyl end (o-c=o) of peptide chain released from it’s tRNA (in P site) by breaking high energy bond–>followed by joining peptide chain to free AA linked to tRNA in A site (peptidyl transferase)
3) conformational change moves mRNA exactly 3 nucleotides through ribosome to prepare ribosome for next aminoacyl-tRNA

REPEAT

32
Q

_________ are necessary for moving the mRNA forward through the ribosome in translation

A

elongation factors (EFS)

33
Q

The end of the protein-coding message is signaled by the presence of one of three stop codons:

A

UAA, UAG, UGA

34
Q

Release factors bind the ribosome with the stop codon in the A site and forces peptidyl transferase to….

A

add a water molecule instead of an amino acid to the peptidyl tRNA (c terminal) thereby freeing the carboxyl end of the chain

  • **released into cytoplasm
  • **Large and small subunits separate with the help of a divorce attorney
35
Q

Protein synthesis can occur in the _______ in addition to the ________

A

Rough Endoplasmic Reticulum (RER) + cytosol

**translation in RER allows for quick packaging and transportation in vesicles

36
Q

Tetracycline

A

blocks binding of aminoacyl-tRNA to A site of ribosome

37
Q

Streptomycin

A

prevents the transition from translation initiation to chain elongation and also causes miscoding

38
Q

Chloramphenicol

A

blocks the peptidyl transferase reaction on ribosome

39
Q

Erythromycin

A

binds in the exit channel of the ribosome (E) and thereby inhibits elongation of peptide chain

40
Q

Rifamycin

A

block initiation of RNA chains by binding to RNA polymerase thus preventing RNA synthesis

Genetics (6 decks)

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