5/29/2023 0 Comments Types of rnaLast of all a termination codon like UAA or UAG or UGA and poly A tail (with many adenine type of nucleotides) at 3′. After this a long coding stretch is present on mRNA. This cap is followed by initiation codon (AUG or GUG). 6.26) bears a cap of methylated guanine at 5′ end. Sometimes, it contains several adjacent DNA cistrons and is known as poly- cistronic m-RNA. Normally it carries the codons of single complete protein molecule hence called mono-cistronic m-RNA. Messenger RNA forms a template for protein synthesis. It contains and carries instruction coded in DNA to the cytoplasm and finally becomes attached to ribosomes. It is formed on specific parts of DNA called structural genes as a complimentary copy of one strand of it. On the basis of molecular size and function, the four types RNA are : (i) Messenger RNA (mRNA) (ii) Transfer RNA (tRNA) (iii) Ribosomal RNA (rRNA) (iv) Heterogenous nuclear RNA (hn RNA).
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