The document discusses the cell cycle and how cells divide through mitosis and meiosis. It provides details on the following:
1) The cell cycle consists of interphase and the mitotic phase. Interphase includes the G1, S, and G2 phases where the cell grows and duplicates its DNA.
2) Mitosis and meiosis are types of cell division. Mitosis produces two identical daughter cells through chromosome duplication and separation. Meiosis reduces the chromosome number by half to produce gametes.
3) Chromosomes duplicate and separate through different phases - prophase, metaphase, anaphase, and telophase. Sister chromatids separate in anaphase to move into two daughter cells
CELL CYCLE AND CELL DIVISION
• CELL CYCLE
The orderly sequence of events by which the cell duplicates its contents and divides into two is termed as the cell cycle. The event is genetically controlled. It consists of two periods-(a) interphase (b)mitosis.
• MITOSIS
Occurs in somatic cells. Equational division. Duplicated chromosomes distributed equally to the daughter cells. Consists of 4 stages –prophase, metaphase, anaphase, and telophase.
• MEIOSIS
Occurs in germ cells. Involves two sequential cycles that are meiosis I and meiosis II. There is only a single cycle of DNA replication. Meiosis I is initiated after is S phase. Meiosis involves the pairing of homologous chromosomes and recombination between them. Four haploid cells are formed called germ cells.
CELL CYCLE AND CELL DIVISION
• CELL CYCLE
The orderly sequence of events by which the cell duplicates its contents and divides into two is termed as the cell cycle. The event is genetically controlled. It consists of two periods-(a) interphase (b)mitosis.
• MITOSIS
Occurs in somatic cells. Equational division. Duplicated chromosomes distributed equally to the daughter cells. Consists of 4 stages –prophase, metaphase, anaphase, and telophase.
• MEIOSIS
Occurs in germ cells. Involves two sequential cycles that are meiosis I and meiosis II. There is only a single cycle of DNA replication. Meiosis I is initiated after is S phase. Meiosis involves the pairing of homologous chromosomes and recombination between them. Four haploid cells are formed called germ cells.
The sequence of events by which a cell duplicates its genome, synthesizes the other constituents of the cell and eventually divides into two daughter cells is termed cell cycle
Infer the significance of cell division.
Differentiate a DNA molecule, a chromosome, and a chromatid.
Characterize the phases of the cell cycle and their control points.
Describe the major events associated with stages of mitosis.
Explain the process of cytokinesis.
Learning Objectives
Describe the role of apoptosis in the life cycle of a cell.
Relate cancer as a result of the malfunction of the cell during the cell cycle.
a deeply explained process of cell division, for understanding it thoroughly. i tried to put in all the information i knew and collected. i hope it is helpful or you.
This presentation is about how cell cycle and cell division takes place in plant and animal cell .... and this presentation also includes mitosis and meiosis and significance of it.
The sequence of events by which a cell duplicates its genome, synthesizes the other constituents of the cell and eventually divides into two daughter cells is termed cell cycle
Infer the significance of cell division.
Differentiate a DNA molecule, a chromosome, and a chromatid.
Characterize the phases of the cell cycle and their control points.
Describe the major events associated with stages of mitosis.
Explain the process of cytokinesis.
Learning Objectives
Describe the role of apoptosis in the life cycle of a cell.
Relate cancer as a result of the malfunction of the cell during the cell cycle.
a deeply explained process of cell division, for understanding it thoroughly. i tried to put in all the information i knew and collected. i hope it is helpful or you.
This presentation is about how cell cycle and cell division takes place in plant and animal cell .... and this presentation also includes mitosis and meiosis and significance of it.
1. Describe how variation in meiosis happens and why it is beneficia.pdffashioncollection2
1. Describe how variation in meiosis happens and why it is beneficial? Steps and functions of
mitosis and meiosis? ( I am having a hard time with defining each step in mitosis and meiosis.
There is meiosis I and II and I get confused on the steps with functions. Any ideas how I can
remember?)
TIA :)
Solution
Explanation:-
Variation in meiosis:-
During meiosis in humans, 1 diploid cell (with 46 chromosomes or 23 pairs) undergoes 2 cycles
of cell division but only 1 round of DNA replication. The result is 4 haploidHaving one copy of
each chromosome, or having a single set of chromosomes. Gametes (egg and sperm cells) are
haploid. daughter cells known as gametes or egg and sperm cells (each with 23 chromosomes – 1
from each pair in the diploid cell).
At conception, an egg cell and a sperm cell combine to form a zygote (46 chromosomes or 23
pairs). This is the 1st cell of a new individual. The halving of the number of chromosomes in
gametes ensures that zygotes have the same number of chromosomes from one generation to the
next. This is critical for stable sexual reproduction through successive generations.
Benefits of Meiosis:-
1. New Cell Generation-
The chromosomes created during meiosis are composed of 50% copies of the parent cell and
50% new cells. ‘Â These new cells are produced during the cross-over stages of the cell division
process. ‘Â During this stage half of the genetic material from the parent cell is copied into the
new cells, with the other half having distinct properties and characteristics.
2. DNA Replication
The process of meiosis involves copying or replication of genetic material from the parent cell
into the new cells. ‘Â As much as half of the genetic properties of the parent cell are copied into
the newly-created cells. ‘Â When applied to humans for example, DNA from both parents will
partly be copied onto the cells of their offspring. ‘Â When DNA is copied or replicated, the
offspring will also have similar qualities with either or both of his/her parents.
3. Genetic Variation
With meiosis, only half of the genetic material is replicated into the new cells. ‘Â This simply
means that the remaining half will be composed of unique genetic properties making each cell
different from the other. ‘Â Through this process, humans for example will all have different
genetic material and structure.
With the process involved in meiosis, humans are able to reproduce similar yet distinct offspring.
‘Â The whole process basically explains the fact that babies may share some genetic traits from
their parents but they will also have unique sets of personalities because of their unique genetic
composition.
Meiosis Stages:-
Prophase I
Chromosomes condense, Crossing over occurs
Metaphase I
Homologous chromosomes pair up and align in middle of cell
Anaphase I
Homologous chromosomes pulled apart
Telophase I
Nuclear Envelope reforms
Cytokinesis I
Cell splits into two
Prophase II
Centrioles divide and move to opposite poles
Metaphase II
Chromoso.
A detailed description of molecular level of cell cycle. Its regulation by different checkpoints. The Structure and Function of MPF. Description of MPF discovery.
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1. The Cell Cycle and How Cells Divide
E-CLIP EIS Teaching – Learning Strategies / Procedures
Biology Secondary 6, duration 60 min.
Teacher: Mr.Wichai Likitponrak
4. 4
Phases of the Cell Cycle
The cell cycle consists of
◦ Interphase – normal cell activity
◦ The mitotic phase – cell divsion
INTERPHASE
Growth
G 1
(DNA synthesis)
Growth
G2
5. 5
Cell Division
An integral part of the cell cycle
Results in genetically identical daughter cells
Cells duplicate their genetic material
◦ Before they divide, ensuring that each daughter
cell receives an exact copy of the genetic
material, DNA
20 µm100 µm 200 µm
(a) Reproduction. An amoeba,
a single-celled eukaryote, is
dividing into two cells. Each
new cell will be an individual
organism (LM).
(b) Growth and development.
This micrograph shows a
sand dollar embryo shortly after
the fertilized egg divided, forming
two cells (LM).
(c) Tissue renewal. These dividing
bone marrow cells (arrow) will
give rise to new blood cells (LM).
7. 7
Chromosome Duplication
0.5 µm
Chromosome
duplication
(including DNA
synthesis)
Centromere
Separation
of sister
chromatids
Sister
chromatids
Centrometers Sister chromatids
A eukaryotic cell has multiple
chromosomes, one of which is
represented here. Before
duplication, each chromosome
has a single DNA molecule.
Once duplicated, a chromosome
consists of two sister chromatids
connected at the centromere. Each
chromatid contains a copy of the
DNA molecule.
Mechanical processes separate
the sister chromatids into two
chromosomes and distribute
them to two daughter cells.
8. 8
Structure of Chromosomes
The centromere is a constricted region of the
chromosome containing a specific DNA sequence, to
which is bound 2 discs of protein called kinetochores.
Kinetochores serve as points of attachment for
microtubules that move the chromosomes during cell
division:
Metaphase chromosome
Kinetochore
Kinetochore
microtubules
Centromere
region of
chromosome
Sister Chromatids
9. 9
Phases of the Cell Cycle
Interphase
◦ G1 - primary growth
◦ S - genome replicated
◦ G2 - secondary growth
M - mitosis
C - cytokinesis
10. 10
Mitosis
Some haploid & diploid cells divide by mitosis.
Each new cell receives one copy of every
chromosome that was present in the original cell.
Produces 2 new cells that are both genetically
identical to the original cell.
DNA duplication
during interphase
Mitosis
Diploid Cell
11. 11
Mitotic Division of an Animal Cell
G2 OF INTERPHASE PROPHASE PROMETAPHASE
Centrosomes
(with centriole pairs) Chromatin
(duplicated)
Early mitotic
spindle
Aster
Centromere
Fragments
of nuclear
envelope
Kinetochore
Nucleolus Nuclear
envelope
Plasma
membrane
Chromosome, consisting
of two sister chromatids
Kinetochore
microtubule
Nonkinetochore
microtubules
12. 12
METAPHASE ANAPHASE TELOPHASE AND CYTOKINESIS
Spindle
Metaphase
plate Nucleolus
forming
Cleavage
furrow
Nuclear
envelope
formingCentrosome at
one spindle pole
Daughter
chromosomes
Mitotic Division of an Animal Cell
13. 13
Mitosis in a plant cell
1 Prophase.
The chromatin
is condensing.
The nucleolus is
beginning to
disappear.
Although not
yet visible
in the micrograph,
the mitotic spindle is
staring to from.
Prometaphase.
We now see discrete
chromosomes; each
consists of two
identical sister
chromatids. Later
in prometaphase, the
nuclear envelop will
fragment.
Metaphase. The
spindle is complete,
and the chromosomes,
attached to microtubules
at their kinetochores,
are all at the metaphase
plate.
Anaphase. The
chromatids of each
chromosome have
separated, and the
daughter chromosomes
are moving to the ends
of cell as their
kinetochore
microtubles shorten.
Telophase. Daughter
nuclei are forming.
Meanwhile, cytokinesis
has started: The cell
plate, which will
divided the cytoplasm
in two, is growing
toward the perimeter
of the parent cell.
2 3 4 5
Nucleus
Nucleolus
ChromosomeChromatine
condensing
15. 15
Meiosis
Reduces the chromosome number such
that each daughter
Cell has a haploid set of chromosomes
Ensures that the next generation will
have:
◦ Diploid number of chromosome
◦ Exchange of genetic information
(combination of traits
◦ that differs from that of either
parent)
Only diploid cells can divide by meiosis.
Prior to meiosis I, DNA replication
occurs.
During meiosis, there will be two
nuclear divisions, and the result will be
four haploid nuclei.
No replication of DNA occurs between
meiosis I and meiosis II.
Interphase
Homologous pair
of chromosomes
in diploid parent cell
Chromosomes
replicate
Homologous pair of replicated chromosomes
Sister
chromatids Diploid cell with
replicated
chromosomes
1
2
Homologous
chromosomes
separate
Haploid cells with
replicated chromosomes
Sister chromatids
separate
Haploid cells with unreplicated chromosomes
Meiosis I
Meiosis II
16. 16
Meiosis Phases
Meiosis involves the same four phases seen in mitosis
prophase
metaphase
anaphase
telophase
They are repeated during both meiosis I and meiosis II.
The period of time between meiosis I and meiosis II is
called interkinesis.
No replication of DNA occurs during interkinesis because
the DNA is already duplicated.
Prophase I
of meiosis
Tetrad
Nonsister
chromatids
Chiasma,
site of
crossing
over
18. 18
Meiosis II is very similar to mitosis
Cleavage
furrow
PROPHASE II METAPHASE II ANAPHASE II
TELOPHASE I AND
CYTOKINESIS
TELOPHASE II AND
CYTOKINESIS
Sister chromatids
separate
Haploid daughter cells
forming
19. 19
A Comparison of Mitosis and Meiosis
Mitosis conserves the number of chromosome sets,
producing cells that are genetically identical to the parent
cell
Meiosis reduces the number of chromosomes sets from two
(diploid) to one (haploid), producing cells that differ
genetically from each other and from the parent cell
The mechanism for separating sister chromatids is virtually
identical in meiosis II and mitosis
20. 20
MITOSIS MEIOSIS
Prophase
Duplicated chromosome
(two sister chromatids)
Chromosome
replication
Chromosome
replication
Parent cell
(before chromosome replication)
Chiasma (site of
crossing over)
MEIOSIS I
Prophase I
Tetrad formed by
synapsis of homologous
chromosomes
Metaphase
Chromosomes
positioned at the
metaphase plate
Tetrads
positioned at the
metaphase plate
Metaphase I
Anaphase I
Telophase I
Haploid
n = 3
MEIOSIS II
Daughter
cells of
meiosis I
Homologues
separate
during
anaphase I;
sister
chromatids
remain together
Daughter cells of meiosis II
n n n n
Sister chromatids separate during anaphase II
Anaphase
Telophase
Sister chromatids
separate during
anaphase
2n 2n
Daughter cells
of mitosis
2n = 6
A Comparison Of Mitosis And Meiosis