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Gene and the Cell > Translation > Flashcards

Translation Flashcards

1
Q

How is the information content in DNA through RNA, translated into protein?

A

It specifies which mRNA nucleotide sequence corresponds to which amino acid in a protein

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2
Q

What are the three types of RNA involved with translation?

A

mRNA; tRNA; rRNA

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3
Q

How is tRNA different from DNA and RNA in the sense of pairing?

A

There is no direct pairing between the codons and amino acids; an adaptor/interpreter is required

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4
Q

What are the 4 ways in which tRNA can act as an adaptor molecule?

A

Bridges the codon to a specific amino acid; each tRNA becomes covalently linked to one specific amino acid; each tRNA has a triplet anti-codon that recognises one ore more codons in the mRNA by base pairing; tRNAs bring the correct amino acid to the ribosome in response to a specific codon

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5
Q

What are the 3 functions of tRNA?

A

It binds to an amino acid and is then ‘charged’; it associates with mRNA molecules through the anti-codon loop; it interacts with ribosomes

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6
Q

What is tRNA charging?

A

Before an amino acid can be incorporated into a growing polypeptide, it must be attached to tRNA. The charged tRNA will then carry the activated amino acid to the ribosome

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7
Q

Describe the process of tRNA charging

A

Covalent linkage of the tRNA 3’-end to the cognate mino acid; catalysed by an aminoacyl-tRNA synthetase; one enzyme per amino acid which each recognise all iso-accepting tRNAs; linkage of amino acids is via an ester bond to the 3’-OH group of the tRNA

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8
Q

What are the three phases of polypeptide synthesis?

A

Initiation; elongation; termination

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9
Q

What happens during initiation?

A

Initiation of translation occurs when mRNA, tRNA, and an amino acid meet up inside the ribosome. The first tRNA is attached at the start codon

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10
Q

What happens during elongation?

A

The ribosome travels down the message, reads codons and brings in the proper aminoacyl tRNA’s to translate the message out to protein. The incoming aminoacyl tRNA is brought into the ribosome A site, where it is matched with the codon being presented.

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11
Q

What 3 steps happen for each codon in the elongation phase?

A

Aminoacyl-tRNA entry; peptide bond formation; translocation

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12
Q

What happens during aminoacyl-tRNA entry?

A

Recognition by the tRNA anti-codon of the codon in the A site; mediated by the EF-tu; aminoacyl-tRNA enters the A sit, GTP hydrolysis triggers release when aminoacyl-tRNA is correctly bound, release of EF-tu and GTP allows the ribosomes to trigger peptide bond formation

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13
Q

What is EF-tu?

A

A prokaryotic elongation factor responsible for catalyzing the binding of an aminoacyl-tRNA to the ribosome

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14
Q

What is peptide bond formation?

A

It is carried out by the 23S rRNA (a ribozyme). It occurs when A and P sites are appropriately occupied. It generates the new peptide bond (peptidyl-tRNA is now in the A site and deacylated tRNA in the P site)

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15
Q

What is translocation?

A

The deacylated tRNA is ejected via the E-site and the peptidyl-tRNA is moved to the P site together with its codon, the next codon is exposed in the A site

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16
Q

What happens during termination?

A

Release factors (RF1 and RF2) act at the A site and need peptidyl-tRNA in the P site

17
Q

What stop codons does RF1 recognise?

A

UAA and UAG

18
Q

What stop codons does RF2 recognise?

A

UAA and UGA

19
Q

What does RF3 do?

A

It promotes hydrolysis of the completes peptide and expulsion of the deacylated tRNA

20
Q

What is the A site?

A

Where aminoacyl-tRNA binds in response to the next mRNA codon

21
Q

What is the P site?

A

Normally carries peptidyl-tRNA

22
Q

What is the E site?

A

The exit

23
Q

What happens when both the A and P site are occupied?

A

The growing peptide on the P site tRNA is transferred to the amino acid in the A site tRNA and translocation resets the ribosome by moving the new peptidyl-tRNA back to the P site

24
Q

What is the correct stop codon that must be recognised that requires the 3’-end of 16S rRNA?

A

AUG

25
Q

What is a polysome?

A

A strand mRNA with associated ribosomes

26
Q

Is it true that several ribosomes can work together to translate the same mRNA and produce multiple copies of the polypeptide?

A

Yes

27
Q

What happens as a result of translation-transcription coupling?

A

The overall elongation rate of transcription is tightly controlled by translation

28
Q

During transcription of protein-coding genes, what is bacterial RNA polymerase closely followed by?

A

A ribosome that is engaged in translation of the newly synthesised trascript

29
Q

What are the 6 inhibitors of protein synthesis?

A

Chloramphenicol, streptomycin, tetracyclin, puromycin, cycloheximide, diphtheria toxin induce ADP ribosylation of eEF2

Gene and the Cell (10 decks)

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