Mitosis and meiosis

Functional Boilogy

1. Mitosis and Meiosis
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Name:
Muhammad Bin Naseem
Roll Number:
F16-0358
Section:
A
Department:
Department of Agricultural Sciences
University:
University of Haripur
Email:

2. Mitosis and Meiosis
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[email protected]
Submitted To:-
Rasheed Akber



MITOSIS AND MEIOSIS
Mitosis and meiosis:
Two types of eukaryotic cell division
According to the Cell Theory, new cells are created by the division of
existing cells
There are two types of eukaryotic cell division:
Mitosis and meiosis
Examples in the human body:
Mitosis is done to make more of a specific body cell
Meiosis is done by certain cells in ovaries or testes to create gametes (eggs
or sperm)
Interphase:
Preparations for mitosis or meiosis

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A eukaryotic cell has a “laundry list” of preparations it must do to ready for
mitosis or meiosis. The time spent completing the preparations is called
Interphase
An important preparation is the duplication of chromosomes. The two
chromosome copies, called “sister chromatids”, remain together until late in
cell division.
Another preparation is the formation of a protein structure called the spindle,
which begins in late Interphase

Mitosis: Introduction
In mitosis, a eukaryotic cell divides to produce two identical “daughter” cells
Human somatic (body) cells divide by mitosis at some point in their lives,
though at different rates
Some cells, such as skin cells, divide rapidly
Some cells, such as nerve cells, divide extremely slowly
There are two major events in the process of mitosis:
1. Equal division of the cell’s chromosomes
2. Division of the cell’s cytoplasm
Many other cell structures are divided in the process of mitosis, but these
slides will focus on the above two events.

Mitosis: Overview of the process
Mitosis may be divided into the following stages:
Prophase - Start of mitosis
Metaphase - Chromosomes line up in middle of cell
Anaphase - Sister chromatids separate
Telophase - Final steps of chromosome division

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Cytokinesis - Division of cytoplasm
Prophase
In prophase, the cell begins the process of division.
The chromosomes condense
Nuclear envelope disappears
Centrioles migrate to opposite poles of the cell.
Asters and spindle fibers form.
Metaphase
The chromosomes line up at the equator of the cell (metaphase plate), with
the centrioles at opposite ends and the spindle fibers attached to the
centromeres.
Anaphase
In anaphase, the centromeres divide.
At this point, each chromosome goes from having 2 sister chromatids to
being 2 separate chromosomes
The spindle fibers contract and the chromosomes are pulled to opposite poles.
Telophase
In telophase the nucleus actually divides.
The chromosomes are at the poles of the cell.
The nuclear envelope re-forms around the two sets of chromosomes.
Cytokinesis
The division of the cytoplasm.
In animal cells, a Cleavage Furrow forms and separates Daughter Cells
In plant cells, a Cell Plate forms and separates Daughter Cells.
Meiosis

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Meiosis is the division and reduction of the chromosomes of a cell
Daughter cells produced have half the chromosomes as the original cell
Purpose of meiosis is the production of gametes (sex cells)
Stages of Meiosis
Meiosis I
Meiosis II
Meiosis I
Prophase I
Chromosomes visible
Homologous pairs of chromosomes come together to from tetrads
Crossing over occurs when a chromatid of one chromosome in a pair
exchanges a segment of itself with the chromatid of the other chromosome in
the pair
Metaphase I
Homologous pairs line up along the equator of the cell
Anaphase I
Homologous pairs of chromosomes separate and move to opposite poles of
cell
Telophase I
Chromosomes complete their migration to poles of the cell and cytokinesis
occurs

Meiosis II
No new DNA replication takes place
Prophase II
Spindle fibers re-form and chromosome begin to move to middle of cell

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Metaphase II
Chromosomes line up along equator
Anaphase II
Sister chromatids of each chromosome separate and move to poles of cells
Telophase II
The chromatids complete migration nuclei reform and cytokinesis occurs.
Meiosis produces four haploid cells