Question

How does the structure of mRNA relate to its function?

Answer 1

Structure:

RNA is ribonucleic acid and mRNA is messenger ribonucleic acid. The main function of mRNA is to transfer all the genetic information from the DNA to the ribosome present in the cytosol. The mRNA comprises of amino acids recognised by specific codon. It consists of four nitrogen bases called as adenine, guanine, cytosine, uracil and are held together by sugar phosphate backbone.

Transcription- is the process in which the genetic information from the DNA is transferred to the mRNA. This process takes place in the nucleus.The strand of DNA act as a template for synthesis. An enzyme called as RNA polymerase II act as a catalyst. The mRNA carries out the process of protein synthesis in the cytoplasm. When the RNA polymerase reads a copy of DNA it causes the pre-RNA molecule to form into mature RNA. This mRNA molecule is further moved from the nucleus to the cytoplasm and attaches to the ribosomes for protein synthesis. In prokaryotes transcription occurs at 5' end and 3' end is attached to the DNA. The 5' end contains shine Dalgarno sequence and binds the mRNA to the ribosome. In eukaryotes transcription takes place in 3' to 5' direction and ATP is added to the 5' end and a poly A tail is added to the 3' end.

Translation: This process takes place in the ribosome of the cytoplasm. The mRNA nucleotide sequence guides in assembling the protein on the ribosome. The message from the mRNA nucleotide sequence is transferred from nucleus to the cytoplasm.The nucleotide sequence of mRNA is complementary to the nucleotide sequence of the DNA template strand. The ribosome reads the mRNA and translate the message into synthesis of functional proteins. Precursor of mRNA contains introns and exons. The introns are removed before translation and translatable exon are kept intact which code for amino acid sequence of proteins.

In prokaryotes there is only one RNA polymerase enzyme but in eukaryotes there are three RNA polymerases namely I, II, III.