1. Meiosis is a type of cell division that forms four daughter cells from one parent cell, each with half the number of chromosomes. It occurs in two divisions: Meiosis I and Meiosis II. 2. During Meiosis I, homologous chromosomes pair up and may exchange genetic material through crossing over, making each chromatid genetically distinct. This results in four daughter cells each with half the original number of chromosomes. 3. Meiosis II is a division that separates the sister chromatids, resulting in four haploid daughter cells with only one chromosome of each type. This maintains the chromosome number during cell division.

1. Prof-Manjider Singh
Department of botany
Govt college Hoshiarpur

2. What is meiosis
Meiosis means “ to reduce”. It is a type of cell
division that forms four daughter cells from
one parent cell. The diploid Parent cell with
46 Chromosome enters meiosis, it will form
four daughter cells each have 23
chromosomes Term meiosis was coined by
Farmer and Moore,1905.

3.  Meiosis occurs in M Phase of cell cycle just
after interphase.
 Interphase of meiosis and mitosis have same
events.
 S phase of meiosis is longer than that of
mitosis.
 Meiosis follows acomparatively shorter or
“no” G2 phase at all.
 Meiosis has two divisions :Meiosis l and
meiosis ll.

4.  Crossing over makes the two chromatids of a
chromosome genetically different from each
other.
 Meiosis ll is also known as homotypic or
homoeotypic or equational division
 Meiosis ll maintains the chromosome number
of the daughter cells.

5.  The cells that enter the meiotic division are
called meiocytes.
 Animals have two typess of meiocytes:
spermatocytes and oocytes.
 Higher plants have two types of meiocytes:
microsporocytes and macrosporocytes.
 Depending upon the stage of the life of
organisms when meiosis occurs there are
three types of meiosis :
 Gametic, zygotic and sporic.

6. Gametic Meiosis Zygotic meiosis Sporphytic meiosis
Gametes
zygote
Meiosis occur
during sporogenesis
Occur during
gametogenesis
Meiocytes(2n)
to
Haploid
(n)gametes
Diplontic life
cycle
Haplontic life cycle Sporogenesis is the
process of formation
of megaspore and
microspore

7.  Meiosis l is the heterotypic or reductional
division.
 It has four stages – Prophase l, metaphase l,
anaphase l and telophase i.
 Prophase l is complicated and longer stage of
meiosis l.
 It has 5 sub phases – leptotene, zygotene,
pachytene, diplotene and diakinesis.

8.  Leptotene ia derived from greek word:
leptos- slender + tainia _ band
 1st stage of Prophase and follows G2 Phase of
interphase
 There is enlargement of nucleus.
 Condensation of chromatic fibres of
interphase nucleus.
 Shortening and elongation makes the
chromosomes to become clear.

9.  Ends of chromosomes attached to nuclear
envelope through attachment plate.
 Though each chromosome has two sister
chromatids, but presence of nucleoprotein
core between them makes the sister
chromatids indistinguishable.
 The peculiar bouquet stage is feature of
leptotene stage of many animal cells.

10.  the chromosomes attach themselves by their
ends (telomeres) to the inner membrane of
the nuclear envelope

12. Zyotene – Joining of two chromosome by synptonemal complex

14. Synaptinemal
complex
Chromosome

16.  Synaptinemal complex formed during zygotene
 Completed by beginning of pachytene
 Disappear in late Pachytene and early Diplotene.

22. Recomination
nodule
Crossing over site

26. Simplified diagram of Diplotene and Diakinesis