Answer:
Robert
Brown discovered nucleus in the cell in 1831.
The nucleus is the control center of a cell. (1)
Structure of Nucleus
(i) Nuclear membrane The nuclear membrane encloses
the nucleus in eukaryotes. The nuclear membrane is penetrated by large nuclear
pore complexes, which selectively transport molecules into or out of the
nucleus.
(ii) Nucleoplasm It is the protoplasm in the nucleus
and contains genetic material chromosomes (DNA) and nucleolus.
(iii) Chromatin The chromatin material inside the nucleus
is an organisation of DNA and protein.
As a cell prepares to divide, the chromatin condenses,
becomes thick enough to form specialised structures called chromosomes.
(iv)Nucleolus It is the most important site of RNA
synthesis. The nucleolus was first recognised by Fontana in 1874.
(2)
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