Describe the structure of a nucleosome. (2)
OR
Mention the evolutionary significance of the following organisms :
(a) Shrews
(b) Lobefins
(c) Homo habilis
(d) Homo erectus
CBSE Class XII Biology Question Paper 2017
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The nucleosome core particle contains two copies of each histone protein (H2A, H2B, H3 and H4) and 146 basepairs (bp) of superhelical DNA wrapped around this histone octomer. It represents the first order of DNA packaging in the nucleus and as such is the principal structure that determines DNA accessibility.
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