Elongation in translation

[Doa110]

---

Members do not see this ad.

What's the order of elongation in translation?

According to AP Cliff, the elongation starts after the first aa-Met has arived at the P site, which would be after codon recognition. Then when the 2nd aa arives at the A site, and translocates to attach to the first aa, elongation starts. It appears that codon recognition is the initiation step right?
So why Acheiver has the it ordered this way: Codon recognition-polypeptide chain -translocation.

Which one is it?

 

[jbravo12]

Achiever is correct. I'm not sure what Cliff's is saying.

1) Codon recognition occurs when tRNA attaches to the A site.
2) Polypeptide chain grows on the tRNA in the P site.
3) Translocation occurs when that growing polypeptide chain moves to the tRNA in the A site. The now free tRNA is released through the E site, and the tRNA with the polypeptide chain moves to the P site.

 

[Doa110]

Achiever is correct. I'm not sure what Cliff's is saying.

1) Codon recognition occurs when tRNA attaches to the A site.
2) Polypeptide chain grows on the tRNA in the P site.
3) Translocation occurs when that growing polypeptide chain moves to the tRNA in the A site. The now free tRNA is released through the E site, and the tRNA with the polypeptide chain moves to the P site.

Thanks. So when is the initiation step?
The question is specifically asking about elongation step.

 

[sunshine222]

Maybe I'm confused about what you're asking, but (from what I remember) the initiation step comes before all that:

Initiation: formation of ribosome complex, binding of mRNA
Elongation: codon recognition, etc.. (all the things you mentioned)
Termination: release of the polypeptide strand, dissembling of the ribosome

Pretty sure that's how it works. Does that answer your question?

 

[Doa110]

yep, I got it. Thanks.