CLASS – IX-X
SUBJECT- BIOLOGY
Chapter- 3
Cell Division
Somatic Cell:
Somatic cells are all the cells in a multicellular organism's body that
are not germ cells (sperm and egg cells). They form the body's
tissues, organs, and various parts. Somatic cells are typically diploid,
containing two sets of chromosomes, one from each parent.
Gametic Cell:
A gametic cell, also known as a sex cell or reproductive cell, is a
haploid cell involved in sexual reproduction. In animals, female
gametes are called ova (or egg cells) and male gametes are called
sperm. These cells have half the number of chromosomes compared
to somatic (body) cells, and they are produced through meiosis.
Cell Division:
Cell division is the process by which a parent cell divides into two or more
daughter cells.
Type of cell division:
3 types- a. Amitosis b. Mitosis c. Meiosis
Mitosis:
Mitosis
is
a
fundamental
process
in
eukaryotic cell division that results in two
genetically identical daughter cells with
the same number of chromosome as their
mother cells. It is known as equational cell
division. In this division, chromosomes and
Mitosis Cell Division:
5 Stages of Mitosis Division :
1.Prophase
2.Prometaphase
3.Metaphase
4.Anaphase
5.Telophase
1. Prophase:
# Nucleus become larger in this
stage.
#
Chromatin
fibers
start
condensing into short , thick and
coiled known as chromosome.
2. Prometaphase:
# Nuclear membrane and
Nucleolus start to degenerate
and disappear.
# Spindle apparatus is formed
with two poles and equatorial
region.
3. Metaphase:
# Nuclear membrane and
Nucleolus start to degenerate and
disappear.
# All chromosomes assemble at
equatorial region from the two
poles.
# In this stage, chromosomes look
short and thick.
# Division of centromere starts.
Anaphase:
# Each chromosome, splitting into two, moves to the two
poles.
# The cleaved centromere moves to the poles, while the
chromatids trail behind.
# Chromosomes look V,L,J,I shaped and these
chromosomes known as metacentric, submetacentric,
acrocentric, telocentric
During Telophase:
# Chromosomes again starts to become thin and long.
# Nuclear membrane and Nucleolus reappear.
# Two new nuclei are formed in two poles
# Spindle apparatus disappear.
Fertilization: The process of combining the male gamete, or sperm, with the
female gamete, or ovum. The product of fertilization is a cell called a zygote.
Chromosome: A structure found inside the nucleus of a cell.
A chromosome is made up of proteins and DNA organized into genes. Each
cell normally contains 23 pairs of chromosomes.
Heredity :The process by which the features of an organism are passed on
from one generation to another is called heredity. The process is done by
genes, which define the characters in the organism.
DNA: Deoxyribonucleic acid, or DNA, is a molecule that contains the
instructions an organism needs to develop, live and reproduce. These
instructions are found inside every cell, and are passed down from parents to
their children.
Differences between mitosis and meiosis
Mitosis
Meiosis
1. Divides one time only
Divides two times and
and produces two daughter produces four cells.
cell.
2. Daughter cells have
Daughter cells have half
same number of chromosomes number of chromosomes as
as parent cells.
parent cells.
3. For growth,
For production of gametes
reproduction, repair and
and formation of Species.
asexual reproduction.
3. Crossing over does not Crossing over occurs.
occur.
4. It is occurred only in
It is occurred only in
Significance of Mitosis and
Meiosis:
Mitosis
Meiosis
1 Growth of the body
To keep Chromosome
number constant in
species to species.
2 Maintain equality
of chromosome
number.
To maintain the
individual characters
of the species.
3 Keeping size and
shape of the cell
Origin of new species.
Short Questions:
What is cell division?
What is mitosis?
What is meiosis?
What is tumor and cancer cell?
What is karyokinesis?
What is cytokinesis?
What is interphase?
What do you mean by haploid and diploid cell?
H. W.
1. Describe mitosis?
2. Describe meiosis.
3. Describe the significance of meiosis.
4. Define chromosome, DNA, Heredity, RNA, Daughter cell,
Zygote, fertilization
5. Chromosome is known as physical basis of heredityExplain.
6. Explain- The features of organism are retained in the
successive generation by meiotic/meiosis cell division.
7. Write down the differences between mitosis and
meiosis.
8. Describe 5 stages of Mitosis with figure.
9. Describe the significance of mitosis.
10. How does cancer cell produce?
11. What do you mean by equational cell division and
reductional cell division?
Prepared by
Shamsun Nahar
Senior Teacher
Subject-Biology
Ph- 01716688916