1) Comparison between prokaryotic mRNA (polycistronic) and eukaryotic mRNA (monocistronic)
- note that 5' UTR and 3' UTR is present in both prokaryotes and eukaryotes. The 5' UTR in prokaryote is important as it contains the Shine-Dalgarno sequence, while the 5' UTR in eukaryotes is important as it can regulate translation as regulatory proteins can bind to it and prevent binding of ribosomes so as to carry out translation.
- note that unlike the prokaryotes, there is RNA processing in eukaryotes. Hence eukaryotic mRNA contain the 5' GTP cap (important for recognition/binding by eukaryotic ribosome and prevent mRNA degradation) and the 3' poly A tail (facilitate export of mRNA from nucleus and prevent mRNA degradation)
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2) Another picture showing that the prokaryotic mRNA is polycistronic.
- The Shine-Dalgarno sequences (impt for recognition and binding of prokaryotic ribosomes) are in between the multiple start and stop codons on the prokaryotic mRNA.
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3) Another diagram that shows the Shine-Dalgarno sequences on prokaryotic mRNA more clealy.
- Since the prokaryotic mRNA has multiple ribosome binding sites called Shine Dalgarno sequences, thus can lead to the synthesis of several different polypeptides. This is unlike the eukaryotic mRNA with only one ribosome binding site/ start site, so it can only lead to the synthesis of one polypeptide.
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hi miss teong
ReplyDeletei'd like to ask a qn regarding the bacteria lecture notes. pg 12 about specialised transduction: "Occasionally envt factors can induce a switch in the phage replication mode from lysogenic to lytic". does that mean from this point generalised transduction takes place (since generalised transduction only occurs during lytic life cycle)? so specialised transduction only consists of the recognition, attachment and infection of bacterial host cell, which results in the subsequent integration of viral DNA into the bacterial chromosome and later replication and passing on of phage DNA? And pg 13: the diagram shows specialised transduction but why does it begin with induction of lytic cycle? i thought specialised transduction occurs during lysogenic life cycle?
thanks.
hsinfen
Hi Hsin fen,
DeleteCan I suggest that we meet face to face? Easier to explain :)
Ms Teong
can you give me a few more days to consolidate more qns? maybe i can meet you on thur (1 nov) after school? -hsinfen
ReplyDeletehi ms teong i have a quick qn. do the 2 types of transcription factors bind to the promoter and enhancer respectively at the same time? and just to confirm, is it both during initiation of transcription? thank you. hsinfen
ReplyDeleteHi Hsin Fen,
DeleteI'm not sure if there is a straightforward answer to that but I would say that the specific TFs bind either before or at the same time as the general TFs. I think it is more impt to understand the effets of their binding than their timing per se. But you can certainly google it if you are interested to find out more.
Yup, you can say that both are involved in initiation.
Ms Teong