a) There junction of the 3\' end of exon 1 and the 5\' end of exon 2 of this gen
ID: 56180 • Letter: A
Question
a) There junction of the 3' end of exon 1 and the 5' end of exon 2 of this gene is somewhere between 201^st and 210^th nucleotides of the mRNA. Can you tell exactly where it is? Please explain your logic briefly.
b) The polyadenylation signal of this gene is somewhere between the 871^st and 931^st nucleotides. Can you tell exactly where it is? Please explain your logic briefly.
c) The sequence above corresponds to the mRNA of human pyridoxal kinase. If the ribosome can sellect one of the ATG s shown above, which one will it select? Please EXPLAIN your logic briefly.
Explanation / Answer
Splicing of the precursor RNA to form mature mRNA.The removal of intron sequences from the primary transcript is carried out on spliceosomes using the donor splice site GU and the acceptor splice site AG located at the exon-intron boundary. A residue at the branch point combines withG at the donor exon intron junction. This reaction results in the release of exon1 and the formation of an intermediate lariat structure with exon 2. In step 2, exon 1 is joined or spliced to exon 2, and the lariat is released.
In the primary transcript within 3' UTR is the AAUAAA poly A addition signal. at 3' end nuclease cleaves RNA 11-30 nucleotides past this site. An enzyme poly A polymerase recognizes the poly A addition signal and adds residues of adenosine to the end of the mRNA to yeild molecules of RNA that have 50-200 adenine residues at 3' end.
Translation is the process by which the ribosomes translate the information in mRNA into protein. On the mRNA Met-tRNA is bound at AUG (T-U) and the adjacent to it the secondaminoacyl-t RNA,phe-TRNA is bound at UUU in the presence of enzyme paptidyltransferase a peptide bond is formed, thus synthesis of protein continues to completely translate the mRNA.
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