1. Meiosis

2. Lesson Objectives
(a) identify, with the aid of diagrams, the
main stages of meiosis (Names of the
sub-divisions of prophase are not
required)
(b) state how meiosis and fertilisation can
lead to variation
Use the knowledge gained in this section
in new situations or to solve related
problems.

3. Recap
Mitosis Meiosis
Same/different Same no. as Half the no. of
no. of parents chromosomes
chromosomes
(with regards to their
parent cells)
Genetically Genetically Genetic
identical to identical variation
parent cell?

4. How do we remember the stages of
the cell cycle?
I nterphase
P rophase
M etaphase
M
A naphase
T elophase
C ytokinesis

5. Overview of Mitosis

6. Overview of Meiosis
• Is a form of nuclear division such that the daughter nuclei
produced contain half the number of chromosomes as the
parent nuclei
• consists of 2 stages: Meiosis I and Meiosis II

7. Meiosis I (pg. 346 Bio Textbook))

9. Meiosis II

10. Questions:
• Is there any similarity between meiosis
and mitosis?
• State the 2 processes that take place in
meiosis that brings about genetic
variation.

11. How is prophase I of meiosis
different from prophase of mitosis?
1. Homologous chromosomes pair up (synapsis)
forming a tetrad (a.k.a. bivalent)
2. Formation of chiasmata. Crossing over takes
place

12. Chiasmata (plural)
(singular)

13. Crossing Over

14. Independent Assortment

15. Sperm production
23
chromosomes
haploid (n)
23
chromosomes
haploid (n)
46 chromosomes 23
diploid chromosomes
(2n)
haploid (n)
23
chromosomes
haploid (n)
Definition of gamete: A reproductive cell containing the
haploid number of chromosomes

16. Production of Eggs
23
chromosomes
haploid (n)
46 chromosomes
diploid (2n)
Variations in the gametes, together with random fertilization
produce variations in the offspring

17. Sexual Reproduction
fertilization
Sperm + ovum zygote
(n) (n) (2n)
formed by meiosis in mitosis
the gonads, testes and
ovary
embryo
(2n)
where n = haploid; 2n = diploid

18. That is why…

19. Test yourself
• Attempt the MCQ worksheet given to you
to assess your understanding of the
lesson