Which bonds are indicated by X and Y in the given diagram ?

Options

A. `{:(X,Y),("Glycosidic bond", "Hydrogen bond"):}`
B. `{:(X,Y),("Phosphodiester bond", "Hydrogen bond"):}`
C. `{:(X,Y),("Glycosidic bond", "Phosphodiester bond"):}`
D. `{:(X,Y),("Phosphodiester bond", "Glycosidic bond"):}`

Answer

B

Explanation

Given figure represents a part of DNA molecules, in which phosphoric acid groups and deoxyribose sugars are linked together by means of phosphodiester bonds. The two DNA chains are antiparallel, i.e., they run parallel but in opposite directions. In one chain the direction is `5' rarr 3'` while in the opposite one it is `3' rarr 5'`. The chains are held together by hydrogen bonds between their bases. Adenine (A), a purine of one chain lies exactly opposite to thymine (T), a pyrimidine of the other chain . Similarly, cytosine (C), a primidine lies opposite to guanine (G) a purine. Three hydrogen bonds occur between cytosine and guanine `(C equiv G)` at positions `1'-1', 2'- 6'` and `6' -2'`. There are two such hydrogen bonds between adenone and thymine `(A=T)` which are formed at positions `1'-3'` and `6'-4'`. Hydrogen bonds occur between hydrogen of one base and oxygen or nitrogen of the other base.