NEET Botany Molecular Basis of Inheritance Questions Solved

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Describe the structure of a RNA polynucleotide chain having four different types of nucleotides.         (3)

RNA is ribose nucleic acid.

1. It has only one polynucleotide chain. Chain has 5'3 polarity.

2. In RNA 4 nitrogenous bases are present: Adenine, guanine, uracil and cytosine.

3. Backbone of RNA is made of ribose-pentose sugar and a phosphate group.

4. A nitrogenous base is linked to the pentose sugar through a N-glycosidic linkage to form a nucleoside such as adenosine, guanosine, cytidine and uridine.

5. When a phosphate group is linked to 5'-OH of nucleoside through  phosphodiester linkage, a corresponding nucleotide is formed.

6. More nucleotides are joined to form a polynucleotide. RNA has a single chain of polynucleotide.

7. A polymer has at one end a free phosphate moiety at 5'-end  of ribose sugar , 5'-end of polynucleotide chain, at the other end to the polymer has a free 3'-OH group which is referred to as 3'-end of the polynucleotide chain. 

8. The nitrogenous bases linked to sugar moiety project out from the backbone. 

                                                                                                  (3)

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