Mitosis and meiosis are two types of cell division. Mitosis produces two identical daughter cells during normal cell growth and reproduction, while meiosis results in four haploid cells with half the number of chromosomes, used to produce gametes like eggs and sperm. Meiosis has two divisions, meiosis I and meiosis II. Meiosis I separates homologous chromosome pairs, while meiosis II separates sister chromatids. This ensures genetic diversity in offspring through independent assortment and crossing over of chromosomes during meiosis I.

2. MITOSIS
CELL DEVISION
OMER GHAFFAR
ANIMAL PRODUCTION AND TECHNOLOGY
180103801

3. CELL CYCLE;
The cell undergoes a sequence of changes, which involves period of
growth, replication of DNA, followed by cell division. This sequence of
changes called cell cycle.

4. PHASES;
There are two phase in cell cycle , which is
further subdivided into different sub-phases.
1. INTER PHASE (non apparent division)
 G-1 PHASE
 S - PHASE
 G-2 PHASE
1. MITOTIC PHASE (period of division)

5. Inter-phase;
The period of cell cycle between two consecutive division termed as the inter-phase
or misleading called resting phase.

6. SUB PHASES OF INTER PHASE;
 G1 (1st gap) = small cell is absorbing nutrients, growing &
doing its job (i.e. making proteins)
 S (synthesis) = cell is continuing to grow & duplicates its
DNA (i.e. chromosomes) in preparation for making
duplicate cells during mitosis
 G2 (2nd gap) = cell keeps growing & doing its job (i.e.
making proteins); it grows too big…
solution = divide in 2

7. Why Would a Cell Divide?
 As cells absorb nutrients and get larger, the volume of the cell
increases faster than the surface area
 This means that a cell can no longer absorb nutrients and get
rid of wastes fast enough to support its demands (volume)
 So what’s a cell to do?
 Solution: divide in 2
Surface area for
exchange not great
enough to support cell’s
needs

8. INFORMATION
Different cells divide at different rates:
Most mammalian cells = 12-24 hours
Some bacterial cells = 20-30 minutes even in seconds
How long is one cell cycle?
 Depends on the cell;
skin cells = ~24 hours,
nerve cells = never after maturity,
cancer cells = very short
 Remember: every cell only has a certain # of divisions it
can undergo, then it dies = apoptosis (programmed cell
death)

9. MITOSIS;
 A process of cell duplication, or reproduction, during which
one cell gives rise to two genetically identical daughter
cells. Strictly applied, the term mitosis is used to describe
the duplication and distribution of chromosomes, the
structures that carry the genetic information.
 PHASES;

10. There are four stages in mitosis;

11. Prophase;
-Chromatin condenses visible chromosomes
Appear as sister chromatids held together by
centromere
-Nuclear membrane dissolves
-The centrioles migrate to opposite poles &
fibers form between them

12. Metaphase
-Chromosomes line-up on the metaphase
plate
-Centromeres are attached to spindle
fibers

13. ;Anaphase
 The chromosomes reach the poles
 Nuclear membranes form around
the 2 new nuclei

14. TELOPHASE
 The chromosomes reach
the poles
 Nuclear membranes form
around the 2 new nuclei

15. Cytokinesis
 The cytoplasm distributed equally between
the 2 new cells
 In animals, a cleavage furrow forms from
outside in
 In plants, a cell plate forms from inside out
.Plant
.Animal

16. Mitosis look like Summary of
mitosis

17. Importanc
e Genetic information unchanged
 Asexual reproduction ( in plant and
animal )
 Replacement of cells
 Healing of wounds
 Regeneration
 Growth and Development
 Tissue culture
 Cancer ( Uncontrolled cell division )

18. MEIOSIS
Formation of gametes, division of
the sex cell (egg and sperm)

20. Fertilization
• The fusion of a sperm sperm and egg egg to form a zygote zygote. • A
zygote is a fertilized egg
SPERM N=23
N=23
EGG 2N=46
ZYGOTE

25. Organisms that reproduce Sexually are made up of two
different types of cells.
1. Somatic Cells are “body” cells and contain the normal number of chromosomes called
the “Diploid” number (the symbol is 2n).
Examples would be … skin cells, brain cells, etc.
2. Gametes are the “sex” cells and contain only ½ the normal number of
chromosomes…. called the “Haploid” number (the symbol is n)….. Sperm cells and ova
are gametes
n = number of chromosomes in the set… so….2n means 2
chromosomes in the set…. Polypoid cells have more than two
chromosomes per set…
example: 3n (3 chromosomes per set)

27. Homologous Chromosomes
• Pair of chromosomes (maternal and paternal paternal) that are similar in
shape and size.
• Homologous pairs (tetrads) carry genes controlling the same inherited
traits.
• Each locus (position of a gene) (position of a gene) is in the same position
on homologues.
• Humans have 23 pairs of homologous chromosomes. Homologous
chromosomes.
22 pairs of autosomes
1 pair of sex chromosome

28. 1. Homologues/
homologous
pairs
Why half?
2. 2 goals: reducing the chromosome number by half and shuffling (recombining) the genes

29. What happens during meiosis I?
As previously mentioned, the first round of nuclear division that occurs during the
formation of gametes is called meiosis I. It is also known as the reduction division
because it results in cells that have half the number of chromosomes as the
parent cell. Meiosis I consists of four phases: prophase I, metaphase I, anaphase
I, and telophase I.
What happens during meiosis II?
During meiosis II, the two cells once again cycle through four phases of division. Meiosis II
is sometimes referred to as an equational division because it does not reduce chromosome
number in the daughter cells — rather, the daughter cells that result from meiosis II have
the same number of chromosomes as the "parent" cells that enter meiosis II. (Remember,
these "parent" cells already have half the number of chromosomes of the original parent
cell thanks to meiosis I.)

30. Meiosis does two things -
 1) Meiosis takes a cell with two copies of every chromosome (diploid) and makes cells with a
single copy of every chromosome (haploid).
In meiosis, one diploid cells produces four haploid cells.
 2) Meiosis result in genetic diversity among individuals in same population.
Genetic diversity is important for the evolution of populations and species.
This trick is accomplished through independent assortment and crossing-over.

31. Another Way Meiosis Makes Lots of
Different Sex Cells – Crossing-Over
Crossing-over multiplies the already huge number of different gamete types produced by independent assortment.

32. Human Life Cycle

33. Meiosis
Parent cell – chromosome pair
Chromosomes copied
1st division - pairs split
2nd division – produces 4 gamete
cells with ½ the original no. of
chromosomes
Interkinesis:Short resting
just before Meiosis II

34. Meiosis compared to mitosis
Purpose
Number of cells produced
Genetics of cells produced
Ploidy of cells produced
Where they occur
Somatic cells Sex cells

35. VIII. Gametogenesis

36. The stages of meiotic cell division: Meiosis I

39. Spermatogenesis
Puberty
Average sperm production =
100 million per day

40. Oogenesis
In embryo
At birth
Arrested at
Prophase I
Ovulation
Arrested at
Metaphase II
Meiosis completed
at fertilization
Approximately 400, 000 400 released

43. THANKS FOR ATTENTION