Cytology: Understanding Mitosis

Study Notes

Mitosis is a process where eukaryotic cells duplicate their genetic material (chromosomes) to prepare for division.
Cytokinesis is the division of the cell's cytoplasm into two new daughter cells.
Eukaryotic cells divide multiple times throughout an organism's life; prokaryotic cells divide through binary fission.
Cell division is crucial for embryonic development, growth, and wound healing in animals.
Errors in cell division can cause cell death or cancer.

Before mitosis, the cell creates an exact copy of its DNA material.
During mitosis, the DNA copies are reorganized and packaged into two sets of chromosomes, and then are separated to opposite ends of the cell.
Mitosis is immediately followed by cytokinesis in most organisms, where the cell body divides into two separate cells.
The original cell (mother cell) is identical to the two resulting cells (daughter cells).

Nucleus: Location of DNA within the cell.
Nuclear envelope: Membrane separating the nucleus from the cytoplasm, crucial for cell division.
DNA: Contains the genetic blueprint for cell behavior.
Chromatin: Loosely bundled coil of DNA that is typically present in non-dividing cells.
Histones: Proteins that hold the DNA strand together in chromatin.
Chromosome: Highly organized form of chromatin in a tightly wrapped and knotted rope shape, present during mitosis.
Chromatid: One half of a duplicated chromosome; contain the same genetic information.
Centromere: Proteins that connect two chromatids.
Microtubules: Part of the cell's cytoskeleton, involved in separating chromosomes during mitosis.
Mitotic spindle: An organized collection of microtubules that coordinate the pulling apart of chromosomes during cell division.
Metaphase plate: An imaginary plane equidistant between the cell's poles where chromosomes are lined up during metaphase.

Chromosomes are highly condensed structures of DNA that are visible during cell division.
Each chromosome is composed of two identical chromatids held together by a centromere.
The centromere is the point where the two chromatids are connected.

Mitosis is divided into five sub-phases: prophase, prometaphase, metaphase, anaphase, and telophase.

By late interphase, chromosomes have duplicated but are still loosely packed
The centrosomes have been duplicated and begin to organize microtubules into an aster.

Nuclear envelope fragments.
Microtubules from one pole attach to one kinetochore, while microtubules from the other pole attach to the other kinetochore.

Spindle fibers push sister chromatids until they are all arranged at the metaphase plate, equidistant from the poles.

Centromeres divide, separating the sister chromatids.
Each chromatid is pulled toward the pole to which it is attached by spindle fibers

The cell elongates as free spindle fibers from each centrosome push off each other.
Two nuclei begin to form surrounded by fragments of the parent's nuclear envelope.
Chromatin becomes less tightly coiled.