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Gene Expression – Translation and Summary

by Georgina Cornwall, PhD
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    00:01 So now, let’s take a quick look at a summary of all of this gene expression before we move on or the translational portion at least because in our eukaryotic cell, we have a little bit more complexity.

    00:18 We have transcription where we are making a copy with messenger RNA using DNA polymerase II and we make this copy of messenger RNA.

    00:29 In a eukaryotic cell, we have to do something with that because we have to be ready to go out into the cytosol.

    00:39 So that is where we have messenger RNA processing to make mature mRNA.

    00:44 We chop out all the introns, maybe alternatively, but we chop them out and we add a 5’ cap and poly-A tail to our messenger RNA.

    00:59 It is now mature and ready to go.

    01:03 Once that messenger RNA leaves the nucleus, it is able to be translated.

    01:10 The ribosome will assemble the small subunit and the messenger RNA will assemble with that.

    01:16 The 5’ cap will be the leading end.

    01:21 Recall there is an unstranslated region, so the start codon will be a little distanced down the messenger RNA.

    01:28 Once we get there, we assemble the whole ribosome and we bring in the tRNAs and we begin the process of the elongation cycle.

    01:40 As the polypeptide is elongated, the ribosome is moving along the messenger RNA, sort of chomp, chomp, chomps three base pairs at a time.

    01:50 And when it is time for the end of the sequence, we’ll run into a stop codon and the release factor or termination factor comes into play, drops into the A-site, blows the whole thing up and we release the polypeptide chain and that will go on to do whatever a polypeptide chain is supposed to do.

    02:16 Depending on what it is, it could be insulin, we’ll have some posttranslational modifications.

    02:21 It will be folded into its final form, maybe using chaperone proteins.

    02:26 And if it’s to go, it’s in the endoplasmic reticulum, it will make its way to the outer cell membrane and be released into the blood stream.

    02:34 So that is the fate of our polypeptides.

    02:37 We have now covered how genes are transcribed and translated, so we know what gene expression is all about.

    02:48 Now, you should be able to explain how tRNA charging works and diagram a ribosomal anatomy, how they come together, as well as describe what happened during the initiation, elongation, and termination phases of translation.

    03:08 And finally, you’ll be able to distinguish the differences in bound and free ribosomes as they translate their proteins.

    03:20 Thanks so much for listening. I will see you in the next lecture.


    About the Lecture

    The lecture Gene Expression – Translation and Summary by Georgina Cornwall, PhD is from the course Gene Expression.


    Included Quiz Questions

    1. Chaperons
    2. Ribosome
    3. D-loop of tRNA
    4. 5’cap of the mRNA
    5. 3’ poly-A tail of mRNA

    Author of lecture Gene Expression – Translation and Summary

     Georgina Cornwall, PhD

    Georgina Cornwall, PhD


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