Question

Discuss major components and events in RNA processing, including introns and exons, splicing, the spliceosome, the 5'G-cap, and poly(A) tail.  Describe tRNA structure and function, including how amino acids are attached to tRNAs and how codons are read.  Discuss mechanisms for translation initiation, elongation, and termination.

Answer 1

The RNA produced from transcription is pre mature RNA . This RNA is not functional and it consist of both introns ( non coding) and exons (coding) . Therefore RNA undergoes post transcription modification to form mature RNA. The events in post transcription are:

I. Splicing : in this step, spliceosome complex take part that have RNA and proteins to remove introns using transesterification reaction. The introns are removed and exons are ligated with each other.

II. 5' capping : in this step, guanine nucleotide are added to the 5' end of mRNA. This ensure the protection of RNA from RNAase and help in recognizition of mRNA by ribosome.

III. 3' tail: In this step, the adenine residue are added at 3' end of RNA known as poly A tail.  

tRNA are the type of RNA. They are also called as transfer RNA. It length is 76 to 90 nucleotide . Their function is that they are mediator between messenger RNA and proteins. They have cloverleaf like structure and L shape in 3D structure that help it to attachment to ribosomes . tRNA have anticodon corresponding to Codon present in mRNA and amino acid.

Protein translation include three process

I. Initiation: in this process, tRNA, mRNA and ribosomes come together and work as a unit to perform translation. The first Codon come in the ribosome and tRNA bring amino acid

II. Elongation : in this step, the peptide bond is formed between amino acid

III. Termination: in this step, the stop Codon come and translation stop because tRNA have not any anticodon corresponding to stop Codon.