Mitosis and Meiosis
Mitosis and meiosis are two distinct types of cell division, that take place in asexual and sexual
organisms based on their reproductive capabilities. Learn about the phases involved when this
intriguing process takes place.
Mitosis and meiosis are two very important biological events that take place within organisms. The
phases involved during cell division take place within organisms in a complex array of splitting cells
and replicating of certain genetically infused information. We look into the differences of mitosis vs
meiosis, and how these two govern the development of organisms by creating full-fledged species,
that begin this process all over again within cells during reproduction.
Mitosis Vs. Meiosis
Before we delve further into the phases of these two types of cell division, we first look into what each
one is and how this process takes place.
Mitosis
In this type of cell division, there are two daughter cells that come forth from a mother cell, where
both contain genetic details, of the parent nucleus within their nuclei. Asexual reproduction takes
place with this type of cell division, which aids in two processes namely, 'cell replacement' and 'growth
regeneration'. In multi cellular organisms this happens when eukaryotic cells separate chromosomes
within the nucleus, organelles, cytoplasm and cell membrane. The daughter cells, which are exactly
two fully formed cells take on the characteristics of the mother cell which is then identical.
Meiosis
This type of cell division involves the involvement of the egg cells and sperm, which are 'gametes',
with each cell containing two copies of each chromosome, one from the mother and the other from the
father, which in turn produces four gamete cells, which have a copy each of the chromosome. These
chromosomes have a mix of paternal and maternal DNA, making certain that the progeny, is different
in its genetic framework of either parent.
Stages Involved in Mitosis Vs. Meiosis
We now look into the stages that separate the two occurrences of these types of cell divisions. We
broadly classify here the stages of mitosis and meiosis as well as what takes place when the presence
of gamete are evident.
Mitosis
Stage 1 - Interphase
In this phase, the DNA begins replicating, where the proteins are produced and the centrioles divide.
Within the nucleus, a small spot called the 'nucleolus', is visible, where all these elements are
preparing themselves for the further stages in the division of cells.
Stage 2 - Prophase
Here the chromatin present in the cell, becomes visible as the chromosomes multiply, and the
nucleolus disappears. From the centromeres, fibers extend from the centrioles, as they move toward
opposite points of the cell. The mitotic spindle is then formed as some fibers cross over, to form this
structure. The building blocks are then formed comprising the cytoskeleton, which form the mitotic
spindle. This comprises two chromatids that make the genetic structure of the chromosome.
Stage 3 - Prometaphase
Kinetochores are then created after the proteins attach themselves onto the centromeres, and this
stage is when the nuclear membrane disintegrates which starts off the first step in the prometaphase.
When this happens the elongated fiber spindles from centromeres, link onto kinetochores, where sister
chromatids are then fused. At the cell's center the rest of the fiber spindles stretch and mesh,
attacking onto chromosomes.
Stage 4 - Metaphase
The chromosomes then arrange themselves at the cell's center, where this arrangement is referred to
as the 'metaphase plate'. This moving around of chromosomes to center themselves at the nucleus, is
to ensure that when it splits that each new nuclei will have a copy each of the chromosome.
Stage 5 - Anaphase
During this stage, the paired up chromosomes split at the kinetochores, and make their way to sides
of the cell pole, after the daughter chromosomes, that is the chromatids, pull apart and move away
from the center.
Stage 6 - Telophase
The spindles that pulled apart the daughter chromosomes vanish, and new membranes start to form
around the nuclei of the daughter chromosome. Then from this point, the separating of the cell takes
place, also known as 'cytokinesis', where a fiber ring made up of protein called 'actin', forms the two
separate daughter cells containing a nucleus each, where the membrane holds them intact within.
Meiosis
Prophase 1: Chromatin duplicates start to multiple during this meiosis stage, where each chromosome
contains two parts of sister chromatids.
Metaphase 1: The chromosomes then start to shift themselves to the center of the plate.
Anaphase 1: The homologous chromosomes then separate, where the sister chromatids remain bound
together.
Telophase 1: As the daughter cells start to form, each one has one chromosome type of the
homologous pair.
Presence of Gamete
Prophase 2: Replicating of the DNA doesn't take place.
Metaphase 2: The chromosomes then start to arrange themselves at the center of the cell plate.
Anaphase 2: The sister chromatids disperse to separate poles of the cell, as the centromeres divide.
Telophase 2: After cell division is done with, the end result showcases four haploid daughter cells.
It is important to understand how cell division governs our very systems, and how life is created by
this very process. A good way to see this taking place, would be to find videos that depict the cell
divisions; they're quite fascinating to look upon.
By Naomi SarahLast Updated: 10/5/2011
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