Question

How many of the following statements are incorrect?

(1) Purine nitrogenous base in a nucleotide is attached to pentose sugar by 1,1 glycosidic linkage.

(2) Adenosine is a nucleoside.

(3) Genome of E. coli possess 4.6 × 10⁹ base pair.

(4) Pitch of DNA helix is 3.4 A⁰.

(5) Euchromatin stains light.

(6) RNA is not more stable than DNA.

(7) RNA can mutate at faster rate than DNA.

Answer 1

(1),(2),(5)(7) are correct
(1)-The purine and pyrimidine bases are covalently attached to the pentose sugar ring at the 1’ position. The sugar is 2’-deoxyribose in DNA. The sugars attach to the nitrogen bases at the 1-position of the pyrimidines and at the 9-position of purines. The bond that is formed between the sugar molecules and the nitrogen bases is known as the glycosylic or glycosidic bond.
(2)-Examples of nucleosides include adenosine,
(3)-The 4,639,221– base pair sequence of Escherichia coli K-12 is presented(it is 4,6* 10^6)
(4)-The turns on the double helix occur every 34A˚ or 3.4 nm after ten pairs of nucleotides, this is called the pitch
(5)-In general, euchromatin appears as light-colored bands when stained in G banding and observed under an optical microscope, in contrast to heterochromatin, which stains darkly. This lighter staining is due to the less compact structure ofeuchromatin.
(6)-This hydroxyl group make RNA lessstable than DNA because it is more susceptible to hydrolysis.
(7)-RNA viruses mutate faster than DNA viruses, single-stranded viruses mutate faster than double-strand virus, and genome size appears to correlate negatively with mutation rate.