Read the following statements and choose the set of correct statements :
(a) Euchromatin is loosely packed chromatin
(b) Heterochromatin is transcriptionally active
(c) Histone octamer is wrapped by negatively charged DNA in nucleosome.
(d) Histones are rich in lysine and arginine.
(e) A typical nucleosome contains 400 bp of DNA helix.
Choose the correct answer from the options below:
- A
(b), (d), (e) Only
- B
(a), (c), (d) Only
- C
(b), (e) Only
- D
(a), (c), (e) Only
Examine each claim.
(a) Euchromatin is loosely packed and transcriptionally active. Correct.
(b) Heterochromatin is densely packed and transcriptionally inactive. Incorrect.
(c) The histone octamer carries a net positive charge; the negatively charged DNA wraps around it through electrostatic attraction. Correct.
(d) Core histones (H2A, H2B, H3, H4) are particularly rich in the basic amino acids lysine and arginine. Correct.
(e) A typical nucleosome contains about 200 bp of DNA (146 bp on the core plus linker). The 400 bp figure is incorrect.
Thus the correct statements are (a), (c), and (d).
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