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Biology · 2024 · 3 marks
CBSE 2024 · Region 1 · Set 3 · Q23
(a) Identify the picture given below and name the tool under which it was viewed. (b) What do the dark spots represent in the picture? Explain how…
(a)
Identify the picture given below and name the tool under which it was viewed.
(b)
What do the dark spots represent in the picture ? Explain how and why are they formed.
Marking-scheme solution
(a)
-‘Beads on String’ / Nucleosomes in Chromatin.
-Under Electron microscope
(b)
• Dark spots are – Nucleosomes.
• -$\displaystyle 8$ molecules of positively charged histone proteins are organized to
form histone octamer, and negatively charged DNA is wrapped around it to form nucleosome.
-To accommodate very long DNA helix in nucleus such an organised structure is formed.
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CBSE Class 12 Biology past-paper question from the 2024 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.