The process of Meiosis
What is meiosis?
Meiosis is a type of cell division whereby a diploid cell (somatic cell), undergoes two cell divisions,
and divides to form four dissimilar haploid cells (sex cells). Diploid cells have two sets of
chromosomes, where each chromosome has a homologous partner. Haploid cells have only one set of
chromosomes. Chromosomes in haploid cells have no homologous partner.
The process of meiosis in animal cells:
Meiosis is a type of cell division used to produce gametes or sex cells (sperm and egg cells). A cell
undergoes meiosis will divide twice.
The first division is meiosis I, and the second division is meiosis II.
In the first meiotic division, the number of cells is doubled, but the number of chromosomes is not.
This results in half as many chromosomes per cell. In the second meiotic division, the number of
chromosomes goes does not get reduced.
First meiotic Division
Prophase I
Chromosomes shorten and become visible as two chromatids joined by a centromere.
Homologous pairs of chromosomes are now visible.
The nuclear membrane and nucleolus disappear.
The spindle starts to form.
Chromatids from each homologous pair touch. The point where they touch is called a
chiasma.
DNA is crossed over (swopped) at their chiasma.
The spinner continues to form.
Metaphase I
The spindle extends across the whole cell.
The homologous chromosomes line up along the equator of the spindle in their homologous
pairs.
One chromosome of each pair lies on either side of the equator.
The centromere of each chromosome attaches to the spindle fibres.
, Anaphase I
The spring of fibres shorten and pull each chromosomes of each chromosome pair to opposite
poles of the cell.
Telophase I
The chromosomes reach the pole of the cell.
Each pole has half the number of chromosome present in the original cell.
The cell membrane constricts and divides the cytoplasm in half to form two cells.
Second Meiotic Division
Prophase II
Each cell formed during meiosis I now device again.
A spindle forms in each of the new cells.
What is meiosis?
Meiosis is a type of cell division whereby a diploid cell (somatic cell), undergoes two cell divisions,
and divides to form four dissimilar haploid cells (sex cells). Diploid cells have two sets of
chromosomes, where each chromosome has a homologous partner. Haploid cells have only one set of
chromosomes. Chromosomes in haploid cells have no homologous partner.
The process of meiosis in animal cells:
Meiosis is a type of cell division used to produce gametes or sex cells (sperm and egg cells). A cell
undergoes meiosis will divide twice.
The first division is meiosis I, and the second division is meiosis II.
In the first meiotic division, the number of cells is doubled, but the number of chromosomes is not.
This results in half as many chromosomes per cell. In the second meiotic division, the number of
chromosomes goes does not get reduced.
First meiotic Division
Prophase I
Chromosomes shorten and become visible as two chromatids joined by a centromere.
Homologous pairs of chromosomes are now visible.
The nuclear membrane and nucleolus disappear.
The spindle starts to form.
Chromatids from each homologous pair touch. The point where they touch is called a
chiasma.
DNA is crossed over (swopped) at their chiasma.
The spinner continues to form.
Metaphase I
The spindle extends across the whole cell.
The homologous chromosomes line up along the equator of the spindle in their homologous
pairs.
One chromosome of each pair lies on either side of the equator.
The centromere of each chromosome attaches to the spindle fibres.
, Anaphase I
The spring of fibres shorten and pull each chromosomes of each chromosome pair to opposite
poles of the cell.
Telophase I
The chromosomes reach the pole of the cell.
Each pole has half the number of chromosome present in the original cell.
The cell membrane constricts and divides the cytoplasm in half to form two cells.
Second Meiotic Division
Prophase II
Each cell formed during meiosis I now device again.
A spindle forms in each of the new cells.
