exon,cds, how are they linked? - (Feb/04/2007 )
I am a bit confused. I was trying to find the sequence of my gene of interest and I got the following info from NCBI.
I thought that cds started where the exon started but below you see that 5`UTR is inside the first exon and CDS starts where the 5`UTR ends. What does this mean?
I would be very glad if some of you could explain this to me.
Thank you very muchhh
Lets see if I can remember my basic biology...
the coding sequence doesn't start at the first exon.
The coding sequence is the sequence that actually codes for the protein.
mRNA is composed of exons and introns, which is later edited as the mRNA is exported out of the nucleus. Editing is conducted by the splicesomem removing intron, producing mature mRNA.
Mature mRNA contains regulatory element(s) in the either or both the 5' and 3' UTR. The coding sequence (cds) is sandwiched in the middle. The UTR regulate how stable the mRNA transcript is (ie its lifetime), what translation factor can activate it, and loading of the translation machinery. be it in lambrush configuration or close loop.
So to make a long story short...
No, the mRNA doesn not start with the coding sequence, nor does it contain only sequence to code for protein. mRNA contains nucleotide segments that also code for control, stability, further processing and translation machinery loading of said transcript.
Thank you very much for the reply.
I think I was confused because I somehow remembered that mRNA starts with the coding sequence but now it is clear.