Topic DNA/Genomics Essay - Main Points!

Q) Discuss the significance of mRNA in the formation of protein

Main points
Key idea:	What is messenger RNA (mRNA), how is it formed and its role
· Product of transcription in which template strand of gene is used for syn of mRNA · Via complementary base pairing b/w exposed DNA nucleotides on template and free RNA nucleotides ·  Ref to RNA polymerase catalyzes formation of phosphodiester bonds b/w adj RNA nucleotides · After its syn, mRNA exits nucleus, via nuclear pore, to cytoplasm · Binds to ribo for translation · Coding seq of single-stranded mRNA consists of triplets of bases (codons), each codon codes for 1 aa
Key idea:	Initiation of translation
· Initiation of translation - 1st codon + 2nd codon of mRNA occupy peptidyl-tRNA binding site (P site) + aminoacyl-tRNA binding site (A site) of ribo, respectively · Ref to codons - complementary to anti-codons of transfer RNA (tRNA) carrying specific aa · Ref to 1st codon (AUG) codes for methionine
Key idea:	Elongation and termination of translation
· Syn of peptide bond b/w methionine + 2nd aa · Ribo translocate 3 base downstream of mRNA, 2nd & 3rd codons now occupy P & A sites, respectively · Another tRNA carrying correct aa will bp to 3rd codon where another peptide bond join 3rd aa to carboxyl end of dipeptide before ribo translocate downstream · Process repeats itself until a stop codon (e.g. UAA, UGA and UAG) occupies A site · Stop codon does not code for any aa, but signal termination of translation · Ref to newly syn polypep, ribo dissociate fr mRNA · Throu this process, mRNA codon seq codes for a single polypep
Key idea:	Processing of eukaryotic mRNA
· Alternative splicing that occur during mRNA processing - diff mature mRNAs each coding for a different polypep
Comments: (i) Visualize the answer with the aid of a labelled diagram. (ii) Verbalize the answer + write down the main points w/o referring to the answer (use abbreviations) (iii) Read again within the next 24h & once more within 72h (do not spend more than 10min) (iv) Alternative splicing refers to a process by which the exons of the RNA produced by transcription of a gene are joined in multiple ways during RNA splicing. The resulting different mRNAs may be translated into different polypeptides. Thus, a single gene may code for multiple proteins.