Dr. M. A. Fouad
Lecture 9
Cell division is the process by which cells produce new cells.
All cells are derived from pre-existing cells.
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There are two types of cell division:
Meiosis
Mitosis
• Mitosis:
In mitosis a diploid cell (46 chromosomes) produce two diploid daughter cells (46 chromosomes).
→ i.e. The number of chromosomes remains unchanged.
• Meiosis:
Type of cell division in which diploid cell (46 chromosomes) produce haploid cells (23 chromosomes).
→ i.e. The number of chromosomes is halved.
• It is the process of somatic cell division that
result in the formation of two daughter cells that are genetically identical are genetically identical to each other, and to the parental cell. .
• Mitosis is used for growth and repair
Mitosis
• There are five distinct stages:
➡ Prophase
➡ Prometaphase
➡ Metaphase
➡ Anaphase
➡ Telophase
• Chromosomes begin to condense
• Each chromosome posses two chromatids
• The mitotic spindle begins to forms
condense فثكتي
spindle لزغم
• The nuclear membrane break up allowing the chromosomes
to spread around the cell.
• Each chromosome becomes
attached at its centromere to a microtubule of the mitotic
spindle
spread رشتني
spindle لزغم
attached طبترم
• The chromosomes
become aligned along the equatorial plane of the cell.
• chromosomes are
maximally contracted.
• Each chromosome
resembles the letter X in shape.
aligned ةفوفصم
equatorial يئاوتسا
plane ىوتسم
contracted ةشمكنم
• The centromere of each chromosome
divides longitudinally.
• Sister chromatids separate and move toward opposite poles of the cell.
longitudinally ايلوط
separate لصفنت
opposite داضتم
pole بطق
• The chromatids have separated completely
• the two groups of daughter chromosomes each become enveloped in a new nuclear membrane
• The cell cytoplasm also separates (cytokinesis) resulting in the
formation of two new daughter cells.
There are five distinct stages: Prophase, Prometaphase, Metaphase , Anaphase and Telophase in_______?
____________
A. Mitosis.
B. Meiosis .
C. All of the above.
D. Non of the above.
During mitosis, the chromosomes begin to condense,
and the mitotic spindle begins to form in _______ stage?
A. Prophase.
B. Prometaphase.
C. Metaphase.
D. Anaphase.
During mitosis, the nuclear membrane begins to break up allowing the chromosomes to spread around the cell, in ________ stage?
A. Prophase.
B. Prometaphase.
C. Metaphase.
D. Anaphase
During mitosis, in ________ Stage, The chromosomes become aligned along the equatorial plane or plate of the cell.
A. Prophase.
B. Prometaphase.
C. Metaphase.
D. Anaphase.
During mitosis, in ________ Stage, the centromere of each chromosome divides longitudinally, and the two daughter chromatids separate to opposite poles of the cell.
A. Prophase.
B. Prometaphase.
C. Metaphase.
D. Anaphase.
This image is of _____ stage in mitosis?
A. Prophase
B. Prometaphase C. Metaphase D. Anaphase E. Telophase
This image is of _____ stage in mitosis?
A. Prophase
B. Prometaphase C. Metaphase D. Anaphase E. Telophase
This image is of _____ stage in mitosis?
A. Prophase
B. Prometaphase C. Metaphase D. Anaphase E. Telophase
Which of the following is the correct sequence of mitotic phases?
A. prometaphase, metaphase, anaphase, telophase, prophase B. anaphase, prophase, prometaphase, metaphase, telophase C. prophase, anaphase, prometaphase, metaphase, telophase D. prophase, prometaphase, metaphase, anaphase, telophase E. prophase, prometaphase, metaphase, telophase, anaphase
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• Meiosis is the process of cell division which results in the production of gametes (eggs or sperm).
• Meiosis produces haploid cells different to each other and the parent cell.
• Meiosis occurs in germ cells that produce gametes.
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Meiosis is consist of two cell divisions
• Meiosis I (reduction phase)
• Meiosis II
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Homologous chromosomes separate
Sister
chromatids separate
haploid Meiosis
I
Meiosis II
Diploid
Haploid
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In Meiosis I Homologous chromosomes separate:
46 (2n) duplicated chromosom
es
23 (1n) duplicated chromosomes
→Meiosis I→
23 (1n) duplicated chromosomes
23 (1n) unduplicated chromosomes
In Meiosis II Sister chromatids separate:
→ Meiosis II→
1. After Meiosis I, the resultant cells have:
A. 46 (2n) duplicated chromosomes
B. 46 (2n) non-duplicated chromosomes C. 23 (1n) duplicated chromosomes
D. 23 (1n) unduplicated chromosomes
• Meiosis reduce the chromosome number by half to produce haploid gametes.
• Two haploid (1n) gametes are brought together through fertilization to form a diploid (2n) zygote
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Meiosis
Meiosis
Mitosis
Sister chromatids
separate
Homologous chromosomes
separate
Sister chromatids
separate
Two Identical
Cells
Growth Multicellular organisms increase their size through growth. This growth involves increasing the number of cells through mitosis.
Tissue Repair As tissues are damaged they can recover through replacing damaged or dead cells.
Cell
Replacement
In some parts of body, e.g. skin and digestive tract, older cells are constantly sloughed off and replaced by new ones.
• Production of Gametes
• In male ➔ sperm
• In female ➔ ovum
• It facilitates halving of the diploid number of chromosomes so that each child receives half of its chromosome complement from each parent.
• Generating genetic diversity by:
• Crossing-over occurs between homologous chromosomes.
• Random distribution of chromosomes.
Meiosis I
• Mitosis takes place in somatic cells.
• Meiosis takes place in germ cells during gamete formation.
• Mitosis occurs as a single one-step process and result in two daughter cells.
• Meiosis can be considered as two cell divisions known as meiosis I and meiosis II and usually produces four cells.
Mitosis
Mitosis results in daughter cells having a diploid
chromosome number (the
same number as mother cell).
Meiosis
During meiosis the diploid
count of mother cell is halved so that each daughter cell
(gamete) receives a haploid number of chromosomes.
Mitosis Meiosis
Site (Where) Somatic cell Germ cell Number of
divisions Single division Two division Role Growth and repair Production of gametes
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44
Mitosis Meiosis
Number of
daughter cells 2 4
Genetically
identical? Yes No
Chromosome Number in
daughter cells Same as parent Half of parent Chromosome
Number in daughter cells
46 (diploid)
23
(haploid)
Quizzes
1. Which type of division is used for the production of haploid gametes (ova and sperm)
A. Meiosis B. Mitosis
2. Which type of division is used for used for growth and repair
A. Meiosis B. Mitosis
3. Mitosis _____?
A. Produce haploid daughter cells B. Consists of two cell divisions
C. Occur in germ cells during gamete formation D. None of the above
E. All of the above
4. Meiosis _____?
A. Produce haploid daughter cells B. Consists of two cell divisions
C. Occur in germ cells during gamete formation D. None of the above
E. All of the above
5. In _______ process, the sperm and an egg join to form the zygote
A. Meiosis B. Mitosis
C. Fertilization D. Replication
6. Mitosis results in two daughter cells that are
genetically identical to each other and the parental cell.
A. True B. False
7. Meiosis results in four genetically different daughter cells.
A. True B. False
8. Which of the following results in diploid daughter cells?
A. Meiosis I B. Meiosis II C. Mitosis
Type of division in which the cell with 46 chromosomes (2n) produce two daughter cells, each have 46
chromosomes (2n) is ______
A. Mitosis.
B. Meiosis.
C. All of the above.
D. Non of the above.
Type of cell division in which diploid cell (46 chromosomes) produce haploid cells (23 chromosomes) is _________
A. Mitosis.
B. Meiosis.
C. All of the above.
D. Non of the above.
All of the following are true about mitosis except _________
A. It is used for growth and repair.
B. It produces four daughter cells
C. Daughter cells are genetically identical to the parent cell.
D. It takes place in somatic cells.
________ occurs as a single one-step process,
__________ can be considered as two cell divisions .
A. Mitosis, Meiosis.
B. Meiosis, Mitosis.
C. Mitosis, Mitosis.
D. Meiosis, Meiosis.
