Fertilization is the fusion of male and female gametes to form a zygote. It usually occurs in the fallopian tube of females. The key steps include attraction of sperm to the egg through fertilin and antifertilin proteins, capacitation allowing sperm to penetrate the egg, the acrosome reaction allowing sperm to penetrate the egg's layers, formation of the fertilization cone, resumption of meiosis in the egg, migration and fusion of the male and female pronuclei to form the zygote nucleus, completing fertilization. Fertilization restores the diploid chromosome number and facilitates egg formation through centriole introduction, forming the first cell of the body, the

1. FERTILIZATION

2. FERTILISATION
It is the union of haploid male and
female pronuclei to form zygote
nucleus.
Or it is fusion of male and female
gametes to form zygote.
Usually it occurs in ampulla of
fallopian tube of female in human
beings.

3. STEPS BEFORE FERTILISATION
 Maturity of mates.
 Gametogenesis in mates.
 Copulation at proper time.
 Discharge of semen into female.
 Proper sperm count in semen.
 Proper shape, size & vigour in
sperms.

4. BEFORE FERTILISATION
 Both male and female mates must be
matured or attain puberty.
 Gametogenesis must occured in both.
 They must mate between 14th to 17th day
of menstrual cycle.
 Proper amount of semen must be
discharged into vagina by male. (2 to 4 ml
having 10 crore sperm per ml).
 60 % sperms should have proper shape,
size and structure and 40 % of them must
be vigourous.

5. STEPS OF FERTILISATION
 Attraction of sperm and secondary
oocyte
 Capacitation
 Penetration of sperm into corona
radiata
 Acrosome reaction
 Formation of fertilisation cone
 Resumption of meiosis – II of
oogenesis
 Migration of male pronucleus
 Amphimixis

6. STEPS OF FERTILISATION
 ATTRACTION OF GAMETES
 Secondary oocyte secrete a glycoprotein
named as FERTILIZIN.
 Sperm has an amino acidic receptor for
it named as ANTIFERTILIZIN.
 Antifertilizin is attracted towards
fertilizin and sperm move near egg.
 CAPACITATION
 Coating over sperm, mainly acrosome is
removed and it can accept signals of
fertilizin for movement towards it.

7. STEPS OF FERTILISATION
 PENETRATION OF SPERM
 After contact, sperm can enter corona
radiata and reach zona pellucida.
 ACROSOME REACTION
 At Zona pellucida, acrosome of sperm
breaks and release enzyme
HYALURONIDASE.
 It digests part of head zona pellucida
and vitelline membrane.

8. STEPS OF FERTILISATION
 FORMATION OF FERTILISATION CONE
 At point of contact to sperm, oolemma
forms a reception / fertilisation cone.
 After entry of first sperm, vitelline
membrane thickens and become the
fertilisation membrane that prevents
further sperm entry.
 Oolemma burst at cone, distal centriole
and nucleus of sperm enter into it. Entry
of centriole initiates second maturation
division forming ovum and secondary

9. STEPS OF FERTILISATION
 RESUMPTION OF MEIOSIS–II IN 2O OOCYTE
 Entry of distal centriole of sperm
initiates second maturation division in
secondary oocyte forming ovum and
secondary polar body.
 MIGRATION OF MALE PRONUCLEUS
 After entry, sperm nucleus enlarges to
become male pronucleus and ovum
nucleus become female pronucleus.
 Male pronucleus moves to female
pronucleus along penetration path.

10. STEPS OF FERTILISATION
 If female pronucleus is on same path, it
continue to meet on same path.
 If female pronucleus is not on same
path, it change path to copulation path.
 AMPHIMIXIS
 It is the union of haploid male and
female pronuclei forming deploid zygote
nucleus.
 This completes fertilisation.
 The mother is now said to be pregnant.

11. SIGNIFICANCE OF FERTILISATION
 It restores diploid chromosome number
in zygote from fusion of two haploid
gametes.
 It facilitates formation of ovum by
introducing centriole from sperm to
secondary oocyte.
 It forms first cell of all multicellular
bodies that is Zygote.
 Copulation path makes the axis of
cleavage in zygote.

12. PARTHENOGENESIS
 It is a special mode of sexual
reproduction in which, unfertilised egg
develops into embryo, without
contribution of male.
 Production of females by
parthenogenesis is THELYTOKY.
e. g. Aphid,
 Production of males by parthenogenesis
is ARRHENOTOKY.
e. g. Honey bee drone