Mitosis

Created by

Phoebe Payne

Cards (19)

Chromosome = An organized package of DNA found in the nucleus of the cell
Chromatid = One of two identical halves of a replicated chromosome
Centriole = Paired barrel-shaped organelles located in the cytoplasm of animal cells near the nuclear envelop. Centrioles play a role in organising microtubules that serve as the cells skeletal system. They help determine the locations of the nucleus and other organelles within the cell.
Centromere = A constricted region of he chromosome that separates it into a short arm (p) and a long arm (q). Following DNA replication, the chromosome consists of two identical structures called sister chromatids, which are joined at the centromere.
Spindle = The mitotic spindle is a structure that forms during cell division and separates duplicated chromosomes. Composed largely of microtubules and chromosomes, the spindle also contains numerous proteins whose roles include biochemical and biophysical regulation of mitosis.
Nucleus = A membrane-bound organelle that contains the cells chromosomes
Nucleolus = A region found within the cell nucleus that is concerned with producing and assembling the cells ribosomes. Following assembly, ribosomes are transported to the cell cytoplasm where they serve as the sites for protein synthesis.
Mitosis:
Process by which cells duplicate their contents and then separate into two identical daughter cells
Some organisms reproduce asexually by mitosis
Most multicellular organisms use mitosis for:
Growth
Tissue repair
Replacement of cells (e.g. blood cells)
Chromosomes :
The nucleus of all ordinary somatic (body) cells contains chromosomes.
In diploid organisms (like us) there are two copies of each chromosome.
In human body cells there are 23 pairs of chromosomes making a total of 46 chromosomes.
Involves one cell division
Results in two daughter cells
Results in diploid daughter cells (chromosome number remains the same as parent cell)
Daughter cells are genetically identical
Occurs in all organisms except viruses
Creates all body cells (somatic) apart from the germ cells (eggs and sperm)
Mitosis is a continuous sequence but is divided into four stages:
prophase
metaphase
anaphase
telophase
Essentially
chromatids are separated by contraction of spindle fibres.
chromatids are pulled to opposite poles of the cell.
the cell then divides.
Each chromatid contains identical genetic information so each daughter cell also contains identical information.
Centrioles:
In most animal cells but are absent from plant cells and yeast
Pair of centrioles located in the centrosome
Form part of the microtubule organizing centre (MTOC)
Each centriole is made up of nine sets of microtubule triplets arranged into a cylinder
Prophase: During prophase the chromosomes become more distinct
they coil up
shorten
thicken
take up stain more intensely
The centriole divides and daughter centrioles move to opposite poles of the cell
Spindle starts to form between the two centrioles
Nucleolus becomes less prominent.
Nuclear membrane breaks down
Prophase (early)
Chromosomes coil and condense
Nuclear envelope present
Nucleolus is evident
Prophase (late)
Chromosome clearly visible as two chromatids joined at the centromere
Nuclear envelope disappears
Nucleolus disappears
Metaphase:
Centrioles have moved to opposite poles
Chromosomes have arranged themselves on the equator of the cell (metaphase plate)
The spindle fibres are attached to the centromeres of the chromosomes
Anaphase:
Centromere of each pair of chromatids splits
Motor proteins walk along the tubulin of the spindle fibres pulling the chromatids to the opposite poles
Chromatids assume a V-shape because the centromere leaves first
Telophase:
Separated chromatids reach the poles
A new nuclear membrane reforms
The cell now contains two identical nuclei
Cytokinesis:
After mitosis, the cell splits into two
In animal cells, cell membrane folds inwards (invaginates)
In plant cells, an end plate forms at the equator and a new cell membrane and cell wall is laid down between the two sides