describe the structure of nucleus.

The nucleus is enclosed by a double layered cellular membrane called the nuclear membrane.

The nucleus contains a nuclear sap, enclosed by the nuclear envelope, which is known as the nucleoplasm. This holds the nucleoli and suspends the chromatins.

The nucleolus is a sub-organelle present inside the nucleus. It can be observed as a dark spot under the microscope.

Nucleoli are made up of proteins, ribosomal RNA (rRNA), and ribosomal DNA (rDNA).

DNA gets associated with protein molecules to form chromatins.

Chromatins are present in the nucleoplasm.

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explanation:

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prophase: we can observe the chromosomes to coil up and condense. they become visible. nuclear membrane and envelope disintigrate.s

metaphase: chromosomes align at the center, the metaphase plate. spindle fibers attach to centromeres of the sister chromatids. they meet at kinetochores.

anaphase: sister chromatids are pulled towards each opposing centromere, set on different poles.

telophase: chromosomes are now clustered up only on either sides of the cell. nuclear membranes reform, and a new cell wall forms along the cell plate. this will lead to cytokinesis, the process that divides the cell membrane and forms the cell wall.