Question 1

What are the main parts of the nucleus?

Accepted Answer

The nucleus contains a nuclear envelope, nucleoplasm, chromatin and a nucleolus. The envelope regulates exchange between the nucleus and cytoplasm through nuclear pore complexes.

Question 2

Why is the nuclear envelope called a double membrane?

Accepted Answer

It consists of an inner membrane and an outer membrane separated by a perinuclear space. The outer membrane is continuous with the endoplasmic reticulum, while nuclear pores perforate the envelope.

Question 3

What is the function of the nucleolus?

Accepted Answer

The nucleolus is a non-membranous nuclear structure where rRNA is synthesized and ribosomal subunits begin to assemble. It is prominent during interphase and disassembles during mitosis.

Question 4

How does chromatin differ from a metaphase chromosome?

Accepted Answer

Chromatin is DNA associated with histones and is relatively uncondensed during interphase. During cell division it condenses into chromosomes, with each metaphase chromosome containing two sister chromatids joined at the centromere.

Question 5

How are chromosomes classified by centromere position?

Accepted Answer

A central centromere produces a metacentric chromosome, a slightly off-centre position produces a submetacentric chromosome, a near-end centromere produces an acrocentric chromosome, and a terminal centromere produces a telocentric chromosome.

The Nucleus — Envelope, Nucleolus, Chromatin and Chromosome Types

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