By means of annotated diagram, give and illustration account of mitosis

Here's an annotated illustration account of mitosis:

Diagram:

Imagine a cell. We'll show key structures changing through the stages.

• Interphase (Before Mitosis):

  • The cell grows and duplicates its DNA.
  • Chromosomes are in a relaxed, thread-like form called chromatin.
  • The nucleus is intact, with a nucleolus visible.
  • Centrosomes (containing centrioles in animal cells) are present.

• Prophase:

  • Chromatin condenses to form visible, duplicated chromosomes, each consisting of two identical sister chromatids joined at the centromere.
  • The nuclear envelope begins to break down.
  • The nucleolus disappears.
  • The spindle fibers (made of microtubules) start to form from the centrosomes, which move towards opposite poles of the cell.

• Metaphase:

  • The nuclear envelope has completely disappeared.
  • The spindle fibers attach to the centromeres of each chromosome.
  • Chromosomes are aligned along the metaphase plate (an imaginary plane equidistant from the two poles).

• Anaphase:

  • The sister chromatids separate at the centromere.
  • Each chromatid is now considered an individual chromosome.
  • The spindle fibers shorten, pulling the chromosomes towards opposite poles of the cell.
  • The cell elongates.

• Telophase:

  • The chromosomes arrive at the opposite poles and begin to decondense back into chromatin.
  • New nuclear envelopes form around each set of chromosomes.
  • Nucleoli reappear.
  • The spindle fibers disappear.

• Cytokinesis (Often overlaps with Telophase):

  • The cytoplasm divides.
  • In animal cells, a cleavage furrow forms and pinches the cell in two.
  • In plant cells, a cell plate forms in the middle and grows outward to create a new cell wall.

This process ensures that each new daughter cell receives a complete and identical set of chromosomes.