Q99 / 200 · NEET 2023 (All India) · Chemistry

Given below are two statements :

Statement I: A unit formed by the attachment of a base to 1' position of sugar is known as nucleoside
Statement II: When nucleoside is linked to phosphorous acid at 5'-position of sugar moiety, we get nucleotide.

In the light of the above statements, choose the correct answer from the options given below:

  • A
    Statement I is false but Statement II is true.
  • B
    Both Statement I and Statement II are true.
  • C
    Both Statement I and Statement II are false.
  • Correct answer
    D
    Statement I is true but Statement II is false.

Solution

Nucleosides are the structural subunit of nucleic acids such as DNA and RNA. A nucleoside, composed of a nucleobase, is either a pyrimidine (cytosine, thymine or uracil) or a purine (adenine or guanine), a five carbon sugar which is either ribose or deoxyribose. The base connected to sugar at  position. Nucleotides are building blocks of nucleic acids DNA and RNA. Nucleotides are composed of a nitrogenous base, a five-carbon sugar (ribose or deoxyribose), and at least one phosphate group. Thus, a nucleoside plus a phosphate group yields a nucleotide. 

Hence, the correct answer is option: 'D'.

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