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Biology
Chemistry
Human biology
Although we often use the term mitosis to describe the entire process, cell divisioncell division
The process by which a parent cell divides into two daughter cells.
is not mitosis. Mitosis is the division of the nucleus, the process that ensures that the daughter celldaughter cell
One of the two identical cells produced as a result of cell division.
s produced have identical sets of chromosomechromosome
A chromosome is like a packet of coiled up DNA. Humans have 23 pairs of chromosomes. They are in the nucleus of every human cell.
s. Successful cell division depends on three stages: the replication of the DNA and cell organellesorganelles
A distinct part of the cell, such as the nucleus, ribosome or mitochondrion, which has structure and function.
in interphaseinterphase
The stage of the cell cycle in which replication of the DNA and cell organelles takes place.
, the division of the nucleus in mitosis and the subsequent division of the cytoplasm and formation of new surface cell membranemembrane
A thin, flexible sheet-like structure that acts as a lining or a boundary in an organism.
s and, in plant cells, cellulosecellulose
A complex carbohydrate which makes up plant cell walls.
cell walls which is described in detail on the next page
Key times and places where mitosis takes place include:
Site of mitosis
Development of an embryoembryo
The name for a group of cells that are developing into a fetus. In humans this is from implantation to the 8th week of development.
in animals and plants, followed by fetal development in animals. The single cell produced by gametegamete
The sex cells (ova and sperm) that join together to form a new unique diploid cell in sexual reproduction.
fusion, divides by mitosis forming entire new organisms.
Germinationgermination
The rapid growth of the radical and plumule as a seed begins to develop and the embryo plant emerges from the seed case.
in plants. The rapid growth of the radical and plumule in a germinating seed depends on rapid mitosis.
Growth in animals and plants. In animals mitosis for growth takes place throughout the organism until the animal is an adult and growth stops. In plants mitosis takes place throughout life in growing regions called the meristems.
Replacements as cells wear out. The cells of the skin and bone marrowbone marrow
Found in the centre of bones, it contains adult stem cells which divide and differentiate to produce red and white blood cells.
are sites of active mitosis replacing skin cells and red blood cellsred blood cells
Carry oxygen in the blood. They are also known as erythrocytes.
that only have a limited life.
Repair. When an area of tissue is damaged internally or externally, mitosis is used to repair the damage.
In cells that are not actively dividing it is not easy to identify the chromosomes that carry the genetic information. The DNA is a mass of loosely coiled threads. At this stage the DNA can be replicated. Once a cell starts to divide, the DNA becomes packaged more tightly so the chromosomes become shorter and denser. As they condense, chromosomes will take up stains allowing them to become visible under the light microscope. By the beginning of mitosis, the nucleosomesnucleosomes
The basic subunits of chromatin, made up of DNA strands wrapped around histones that coil around each other tightly at the beginning of cell division.
have coiled and supercoiled to produce the chromosome structure we can see under the microscope.
The loose structure of DNA in a cell between divisions becomes organised into condensed structures visible under the microscope at the beginning of mitosis