1. Overview of Cell Division
Cell division is the process by which a parent cell divides into two or more
daughter cells. It is essential for growth, repair, and reproduction in living
organisms. There are two main types of cell division:
1. Mitosis: Produces two genetically identical daughter cells.
2. Meiosis: Produces four genetically diverse daughter cells (gametes).
2. The Cell Cycle
The cell cycle is the series of events that cells go through as they grow and
divide. It consists of two main phases:
1. Interphase:
o G1 Phase: Cell grows and synthesizes proteins.
o S Phase: DNA replication occurs.
o G2 Phase: Cell prepares for division.
2. Mitotic Phase (M Phase):
o Includes mitosis (nuclear division)
and cytokinesis (cytoplasmic division).
3. Mitosis
Mitosis is the process of somatic (body) cell division, resulting in two
identical diploid (2n) daughter cells. It consists of four stages:
Stages of Mitosis:
1. Prophase:
o Chromatin condenses into visible chromosomes.
o Nuclear envelope breaks down.
o Spindle fibers form and attach to centromeres.
2. Metaphase:
o Chromosomes align at the metaphase plate (equator of the
cell).
o Spindle fibers fully attach to sister chromatids.
3. Anaphase:
o Sister chromatids separate and move to opposite poles of the
cell.
, oSpindle fibers shorten, pulling chromatids apart.
4. Telophase:
o Chromosomes de-condense into chromatin.
o Nuclear envelope reforms around each set of chromosomes.
o Spindle fibers disassemble.
Cytokinesis:
Division of the cytoplasm, resulting in two daughter cells.
In animal cells: A cleavage furrow forms.
In plant cells: A cell plate forms.
4. Meiosis
Meiosis is the process of gamete (sex cell) division, resulting in four
genetically diverse haploid (n) daughter cells. It consists of two rounds of
division: Meiosis I and Meiosis II.
Stages of Meiosis I:
1. Prophase I:
o Chromosomes condense and homologous chromosomes pair up
(synapsis).
o Crossing over occurs, exchanging genetic material between
homologous chromosomes.
o Nuclear envelope breaks down.
2. Metaphase I:
o Homologous chromosome pairs align at the metaphase plate.
o Spindle fibers attach to each homologous chromosome.
3. Anaphase I:
o Homologous chromosomes separate and move to opposite poles.
o Sister chromatids remain attached.
4. Telophase I:
o Chromosomes reach opposite poles.
o Nuclear envelope may reform temporarily.
o Cytokinesis occurs, resulting in two haploid cells.
Stages of Meiosis II:
1. Prophase II:
o Chromosomes condense again.
o Nuclear envelope breaks down.
Cell division is the process by which a parent cell divides into two or more
daughter cells. It is essential for growth, repair, and reproduction in living
organisms. There are two main types of cell division:
1. Mitosis: Produces two genetically identical daughter cells.
2. Meiosis: Produces four genetically diverse daughter cells (gametes).
2. The Cell Cycle
The cell cycle is the series of events that cells go through as they grow and
divide. It consists of two main phases:
1. Interphase:
o G1 Phase: Cell grows and synthesizes proteins.
o S Phase: DNA replication occurs.
o G2 Phase: Cell prepares for division.
2. Mitotic Phase (M Phase):
o Includes mitosis (nuclear division)
and cytokinesis (cytoplasmic division).
3. Mitosis
Mitosis is the process of somatic (body) cell division, resulting in two
identical diploid (2n) daughter cells. It consists of four stages:
Stages of Mitosis:
1. Prophase:
o Chromatin condenses into visible chromosomes.
o Nuclear envelope breaks down.
o Spindle fibers form and attach to centromeres.
2. Metaphase:
o Chromosomes align at the metaphase plate (equator of the
cell).
o Spindle fibers fully attach to sister chromatids.
3. Anaphase:
o Sister chromatids separate and move to opposite poles of the
cell.
, oSpindle fibers shorten, pulling chromatids apart.
4. Telophase:
o Chromosomes de-condense into chromatin.
o Nuclear envelope reforms around each set of chromosomes.
o Spindle fibers disassemble.
Cytokinesis:
Division of the cytoplasm, resulting in two daughter cells.
In animal cells: A cleavage furrow forms.
In plant cells: A cell plate forms.
4. Meiosis
Meiosis is the process of gamete (sex cell) division, resulting in four
genetically diverse haploid (n) daughter cells. It consists of two rounds of
division: Meiosis I and Meiosis II.
Stages of Meiosis I:
1. Prophase I:
o Chromosomes condense and homologous chromosomes pair up
(synapsis).
o Crossing over occurs, exchanging genetic material between
homologous chromosomes.
o Nuclear envelope breaks down.
2. Metaphase I:
o Homologous chromosome pairs align at the metaphase plate.
o Spindle fibers attach to each homologous chromosome.
3. Anaphase I:
o Homologous chromosomes separate and move to opposite poles.
o Sister chromatids remain attached.
4. Telophase I:
o Chromosomes reach opposite poles.
o Nuclear envelope may reform temporarily.
o Cytokinesis occurs, resulting in two haploid cells.
Stages of Meiosis II:
1. Prophase II:
o Chromosomes condense again.
o Nuclear envelope breaks down.
