Figure showing packaging of DNA Helix. Observe the figure and answer the following questions.
Identify the labels A, B and C in the given figure.
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A) DNA (B) H1 histone (C) Histone octamer
In the figure, A is the DNA strand wound around the core; B is the H1 histone that sits outside, where DNA enters and leaves; C is the core of histone molecules, the histone octamer.
Option (1) (A) H1 histone (B) DNA (C) Histone octamer — Incorrect. In the figure, A is the thread wound round the core, which is the DNA. H1 histone (B) sits outside the core on the linker DNA, so A cannot be H1.
Option (2) (A) DNA (B) H1 histone (C) Histone octamer — Correct. In a nucleosome, the negatively charged DNA (A) is wrapped around a core of eight histone molecules, the histone octamer (C). The H1 histone (B) sits on the linker DNA between nucleosomes.
Option (3) (A) Histone octamer (B) DNA (C) H1 histone — Incorrect. A is the DNA strand, not the octamer. The histone octamer is the core (C) round which the DNA is wrapped, and H1 is B.
Option (4) (A) DNA (B) Histone octamer (C) H1 histone — Incorrect. B is H1 and C is the octamer, not the other way round.