Muhammad Taimur Siddique........PAKISTANI

2. Meiosis
• Course Title : Basic Biology
• Presented To : Dr. Pervaiz Anwar
• Reg #767BSBT/F-15

3. •Type of cell division in which number of
chromosome in daughter cell is reduced to half as
compared to parent cell.
•Dipliod(2n) Hapliod(n)
•Meiosis is sexually reproduction
•Meiosis occurs in the sex organs, producing
gametes—sperm and eggs

4. Why do we need Meiosis?
•It is the fundamental basis of sexual
reproduction
•Two haploid (n) gametes are brought together
through fertilization to form a diploid (2n) zygote
•If egg and sperm had the same number of
chromosomes as other body cells then the
offspring would have too many chromosomes

6. MEIOSIS has two distinct stages
•MEIOSIS I consisting of 5 phases:
Interphase I
Prophase I
Metaphase I
Anaphase I
Telophase I.

7. •MEIOSIS II consisting of 4 phases
Prophase II
Metaphase II
Anaphase II
Telophase II.

9. Meiosis II
Interphase
•Cell build up energy
•DNA Replication (to make duplicated
chromosomes
•Cell doesn’t change structurally.
•Centriole pair also replicate

10. • Nucleus and nucleolus visible

11. Prophase I
•This is very prolonged phase, chromosome
behave as homologus chromosome
•It is further divided into following stages
Leptotene
Zygotene
Pachytene
Diplotene
Diakenisis

12. Leptotene
•Chromosome is visible
•Chromosome is shorten & thick
•Size of nucleus increase
•Chromosome is starting getting closer to each
other
•It last for few hour

13. Zygotene
•First essential phenomenon of meiosis is
synapsis(pairing of homologus chromosome
•Paring is highly specific & exactly pointed with
no definite shape
•Each paired complex structure is tetrad
•It last for few hours

14. Pachytene
•Pairing of homologus chromosome is completed
•Chromosome is more and more thick
•Non sister chromatids exchange their segment
due to chismata formation during process called
crossing over
•It last for days,weeks,years

15. Diplotene
•The paired chromosome repled each other and
begin to seprate
•Separation is not complete at chismata
•But separation is not complete they are unite at
one point

16. Diakenisis
•Condensation of chromosome is reach to
maximum
•Sepration is completed
•Chismata is disappear
•Nucleus and nuclear membrane disappear
•Spindle fibers formed

17. Metaphase I
•It is shortest phase
•Chromosomes fully condense.
•Spindle fibers originate
•kinetochore fiber attach to
kinetochore region of
chromosome
•Chromosome align them at
equator
metaphase plate

18. Anaphase I
•Homologous chromosomes
separate and move towards
the poles.
•Sister chromatids remain
attached at their
centromeres.
•This is actually reduction
phase because each pole
receive half the number

19. Telophase I
•Nuclear membrane
reorganize around
each set of
chromosome
•Nucleus and nucleoli
reappear in this phase
•Chromosome
decondense in this
phase

20. Meiosis II
•No interphase in this phase
•There is no synthesis in this phase
•Very short no more DNA replication
•Meiosis II is similar to mitosis

22. Prophase II
•Chromosome condense
•Nuclear envelope
disappear
•Nuclear material released
in cytoplasm and
cytoplasm more viscous
•Nucleoli disappear
• spindle fiber originate

23. Metaphase II
•Spindle fiber bind to
kinetochore of sister
chromatids.
• the spindle fibers
contract and pulling
sister chromatids.
•Spindle fibers aligned at
equator

24. Anaphase II
• It is more critical phase
of mitosis which ensure
equal distribution of
chromatids in daughter
cell
•Sister chromatids are
separated
•Half chromatids travel to
opposite pole

25. Telophase II
•Reaching of
chromosome at each
pole
•Nuclear envelope
reorganize
•Chromosome
decondense
•Nucleoli reorganize as a
result four nucleoli at
each pole

26. Overview