Mitosis

Stages of Mitosis

Alafiya Taher Kapadia

1. Why do cells divide?

2. How do cells divide?

3. Stages of Mitosis

a) Interphase

b) Prophase

c) Metaphase

d) Anaphase

e) Telophase

f) Cytokinesis

Index

Biology is the only subject in which multiplication is the same thing as division…

You started as a cell smaller than

a period at the end of a sentence…

•Where it all began…

• And now look at you…

How did you get from there

to here?

Going from egg to baby….

the original fertilized egg has to divide…

and divide…

and divide…

and divide…

•Getting from there to here…

For reproduction

For growth

from fertilized egg to multi-celled organism

For repair & renewal

replace cells that die from normal wear & tear or from injury

•Why do cells divide?

•Pop quiz

1.What is the importance of cell division?

Growth

Death

Cancer

Mitosis is the division of somatic cells (body cells)It is the process in which the nucleus divides to form two new nuclei.

The chromosomal number remains unchanged.

•How do cells divide?

Somatic Cell

Daughter Cells

•Pop quiz

1. Mitosis in body cells results in _____________.

4 daughter

cells

2 daughter

cells

1dupilcate

cell

• The process of mitosis is fast and highly complex. The sequence of

events is divided into stages corresponding to the completion of one

set of activities and the start of the next. These stages in order of

occurrence are-

• Interphase

• Prophase

• Metaphase

• Anaphase

• Telophase

• Cytokinesis

•Stages of Mitosis

•Pop quiz

1. The order of the stages in Mitosis is

Interphase-Anaphase-Telophase-

Prophase-Metaphase

Interphase-Prophase-Metaphase-

Anaphase-Telophase

Interphase-Metaphase-Anaphase-

Prophase-Telophase

• The cell is in Interphase for most of its life cycle.

• In Interphase, the cell “prepares” for division by

• obtaining nutrients and growing,

• copying its DNA, and

• replicating its centrioles.

• The nuclear membrane is still visible.

• Chromatin has not yet condensed into chromosomes in this stage.

• The nucleolus is still present.

•Interphase

chromatin threads

nucleolus

centrioles

•Pop quiz

1. Body cells are in ________________ stage for most of its life cycle.

Anaphase

Interphase

Prophase

•Pop quiz

1. Body cells are in ________________ stage for most of its life cycle.

Anaphase

Interphase

Prophase

• In Prophase:-

• DNA becomes visible as chromosomes

• Nuclear membrane dissolves

• Centrioles migrate to opposite poles

• Spindle fibers form

•Prophase

chromatids

centrioles

spindle fibers

nucleus

•Pop quiz

1. Spindle fibers form in __________ stage.

Anaphase

Prophase

Metaphase

In Metaphase:-

• Spindle fibers attach to centromeres

• Chromosomes line up at midline of the cell

• This organization helps to ensure that in the next phase, when the chromosomes are separated, each new nucleus will receive only one copy of each chromosome.

•Metaphase

equatorial plane

centromeres

•Pop quiz

1. In Metaphase chromosomes line up along the _________

Equatorial

Plane

Poles

Don’t line up

• In anaphase, the spindle fibres shorten, which splits the chromosome strand into two separate, sister chromatids. The sister chromatids are pulled to opposite ends of the cell.

• This is the only stage in the life of a cell where the chromosome number is greater than a 2n (or diploid) count

•Anaphase

sister chromatids

•Pop quiz

1. Only stage where chromosomal number is greater

than 2n is ___________

Metaphase

Anaphase

Telophase

• The chromosomes finally reach opposite poles (the ends) of the cell.

• The nuclear envelope and nucleolus reform around each new set of chromosomes. The chromosomes disperse and are no longer visible.

• Spindle fibers disperse and are no longer visible.

•Telophase

nuclear envelope

cytoplasm begins to divide

• Cytokinesis marks the end of mitosis in the cell cycle. It is where the cell officially splits into two separate cells, called daughter cells. Each daughter cell now has the same number of chromosomes as the original cell before mitosis. The cell splits when a furrow forms that pinches the cell in two.

•Cytokinesis

contractile ring

centrosome

nuclear envelope

decondensedchromosome

•Pop quiz

1.The chromosome reach the poles of the cell in

___________ stage.

Prophase

Anaphase

Telophase

• Prophase: • Chromosomes condense• Nuclear envelope disappears• centrosomes move to opposite sides of the cell• Spindle forms and attaches to centromeres on the chromosomes

• Metaphase• Chromosomes lined up on equator of spindle• centrosomes at opposite ends of cell

• Anaphase• Centromeres divide: each 2-chromatid chromosome becomes two 1-chromatid

chromosomes• Chromosomes pulled to opposite poles by the spindle

• Telophase• Chromosomes de-condense• Nuclear envelope reappears• Cytokinesis: the cytoplasm is divided into 2 cells

Exit

• Summary of Mitosis