Biomedical Engineering Reference
In-Depth Information
Types of Cell Division: Meiosis/Mitosis
Difference between meiosis and mitosis is that meiosis takes place in gametes
(
germ
-
line cells
) and it is a division with reduction of chromosome number in both
mother's and father's cells, while mitosis occurs in tissues other than gametes
(
somatic
) and during mitosis, the cell's genome is replicated and the cells split once
giving two new identical cells [
13
-
17
]. However, meiosis involves one genome rep-
lication and two cells are splitting, so that four haploid cells are produced from one
parent cell. It occurs in two main stages: Meisosis I and Meisosis II. Chromosomes
exist in pairs. Each partner in the pair has the basic shape, structure, and contains
complimentary genes. There are 23 pairs or 46 chromosomes in humans. A
homolog
refers to the corresponding partner in a pair [
13
-
17
].
Importance of Mitosis
1. Each
homolog
carries information about the same hereditary trait, though the
information may vary: dominant, recessive (blond, brown,) etc.
2. A single pair of homologous chromosomes may carry information for several
thousand hereditary traits.
3. A female has 23 pairs of homologous chromosomes. This includes 22 pairs of
autosomes
, and 1 pair of
sex chromosomes
(
XX
) (
sex chromosomes identical
).
4. A male has 22 pairs of homologous chromosome (autosomes), and 1 pair of non-
homologous chromosomes—
sex chromosomes
(
XY
) (
sex chromosomes
non
-
identical
).
5. During period of time between cell divisions, DNA is in the form of
chromatin
.
When chromatin condenses, chromosomes become visible. Chromosome is
actually 10,000 times longer than when coiled and condensed. Condensing is
necessary to fit in nucleus and separate in cell division.
6. Chromosome structure: two
chromatids
(sister chromatids) attached by
centromere
.
Mitosos is important for repair of somatic cells of individual young or adult
organism
,
since every moment cells are naturally dying in the body and need to be
replaced by new ones with the same function. It is process by which the nucleus
of the cell is divided into two nuclei
,
each with the same number and kinds of
chromosomes as parent cell. Cytokinesis is process by which the cytoplasm
divides
,
forming two distinct cells
.
Importance of Meiosis
1. Meiosis is significant for development of a new organism. Development starts
with a
zygote
with a
2n
of 46. Development is due to mitosis and differentiation.
