From NCERT NEET - 2015
Which one of the following is not applicable to RNA ?
1. Complementary base pairing
2. 5' phosphoryl and 3' hydroxyl ends
3. Heterocyclic nitrogenous bases
4. Chargaff's rule
Ans:4. Chargaff's rule
- In RNA, every nucleotide residue has an additional –OH group present
at 2' -position in the ribose. Also, in RNA the uracil is found at the place of
thymine (5-methyl uracil, another chemical name for thymine).
- DNA as an acidic substance present in nucleus was first identified by
Friedrich Meischer in 1869. He named it as ‘Nuclein’. However, due to
technical limitation in isolating such a long polymer intact, the elucidation
of structure of DNA remained elusive for a very long period of time. It was
only in 1953 that James Watson and Francis Crick, based on the X-ray
diffraction data produced by Maurice Wilkins and Rosalind Franklin,
proposed a very simple but famous Double Helix model for the structure
of DNA. One of the hallmarks of their proposition was base pairing between
the two strands of polynucleotide chains. However, this proposition was
also based on the observation of Erwin Chargaff that for a double stranded
DNA, the ratios between Adenine and Thymine and Guanine and Cytosine
are constant and equals one.
