In this ppt you will clearly get information about how the early embrionic development take place in drosophila,in each and every stage.

1. Early development in
drosophila
By
Name:Ansari Bisma Irfan ul Haque
Msc-1

2. Early development in drosophila:
• Egg is centrolecithal
• After fertilization, series of superficial cleavages
• Blastoderm is syncytial until 13th cleavage (256 nuclei!)
• Nuclei begin dividing centrally, migrate toward the edges
• Several nuclei migrate to posterior end, form cell membranes (pole
cells)
• Give rise to the adult gametes.

3. Superficial cleavage:
Syncytial blastoderm stage:
- zygotic nuclei undergo 8 divisions.
- nuclei migrate to periphery – karyokinesis
continues.
Cellular blastoderm stage:
- following division 13, oocyte plasma
membrane folds inward – partitions off each
nucleus and associated cytoplasm –
constricts at basal end

4. Superficial cleavage:

5. • 1st A-p polarity:
1. nerve cells releases gurken m-RNA(it’s
help in making gurken protein)
2. On follicle cells Receptors present called
Torpedo.
3. Oocyte move toward follicle cells ,which
means it moves opposite to nerve cells .
for this reason gurken and torpedo
association takeplace. The way of association
defines the way of patterning.
1. When gurken & torpedo starts
associating,in result follicle cells start
changing their property
2. Squamous cell ---→coloumnar cell
Axis patterning in
drosophila:

7. 2nd dorsal ventral polarity
A fourth set of maternal genes which defines
dorso ventral axis.Gurken protein is responsible
for the formation of dorsal follicle cells.Gurken &
TorpedoDorsal fateDorsal & PipeVentral
fateMaternal deficiencies of either gurken or the
torpedo gene cause ventralization of embryo.
Gurken is active only in oocyte & torpedo is active
in follicle cells.No Dorsal geneDorsal fate• Dorsal
protein is in highest concentration in ventral
nuclei & responsible for ventral axis.i

8. Maternal gene:
Maternal effect genes (e.g. bicoid, nanos)Establish polarity:- mRNAs
differentially placed in eggs- transcriptional or translational regulatory
proteins; transient- diffuse through syncytial cytoplasm- activate or
repress zygotic genes
Anterior side:Dynein (-ve)
Exupurentia (exu)
Swallow (swa)
↓
Bicoid(BCD)
Bcd promotes HB (hunck back)
And inhibits cd(caudal)
Posterior side:Kinesin(+ve)
Oskar(osk)
Tudar(tu)
↓
Nanos
Nanos Promotes caudal(cD)
&inhibits hunchback (HB)

9. Terminal
gene:(Acron&Telson)
Formed
Acron+Bcd -------→anterior part (Brain)
formed
Telson+Nano ------→Posterior part(Tail)
Torso. ---------→grucho
Groucho is present on middle side.is not
present on most anterior or most dorsal
part.
Torso receptor present on a place where
torso like protien (TLP)is present.Terminal
gene is present on that side.
Acrone is present on anterior side&Telson is
present on posterior side.

10. Zygotic gene(segmentation genes)
• These genes are responsible for
segment formation in Drosophila
• These are zygotic effect genes &
express after fertilization
• Define number, polarity or size
segments.
• Three classes of segmentation genes:
(Gap genes, Pair-rule genes & Segment
polarity genes.)

11. Gap genes:
• These genes divides the
embryo into broad regions.
• Their mutations result in gap
in the embryos segmentation
pattern
• All the gap tranciption
factor.gene proteinsGap
genes are Kruppel, Knirps,
giant, Tailless & hunchback
genes.

12. Regulation of gap genes:
• The gap genes are activated
or repressed by the maternal
effect genes.
• High levels of Hunchback &
bicoid genes induce the
expression anterior gap
genes(giant) while the kruppel
appears when levels of
hunchback genes declines.
• High levels of Caudal at the
posterior side is responsible for
abdominal gap genes ( Knirps &
gt)

13. Paired ruled gene:
• • The protein products of the gap genes
activate the transcription of pair-rule
genes.
• Mutation in these genes, usually.
• delete portions of alternate segments.
• These genes result in the appearance of
a series of stripes.
• These includes: Hairy, Even skipped,
Runt, Fushi tarazu, Odd skipped, Paired,
sloppy paired and odd paired.

14. Regulation of paired rule gene:
• Different concentration of gap
proteins determines the
transcription of pair rule genes.
• Even skipped stripe is controlled
by a region i.e, activated by
Bicoid & Hunchback &
repressed by both Giant &
Kruppel proteins.
• The anterior & posterior border
is maintained by influence from
Giant & Kruppel respectively.

15. Segment polarity gene:
• • The pair rule gene proteins activate
the transcription of these genes.
•
• Even-skipped
•
• Divide the the embryo into 14
segments & provide greater definition
to the stripes.
•
• • These genes includes: Wingless,
Cubitus interruptus, Patched,
Engrailed, Hedgehog & Armadillo

16. Regulation of segment polarity gene:
• • Expression of Wingless (Wg) and
engrailed (En) is initiated by pair
rule genes.High amount of Even
skipped (eve) or Fushi tarazu (ftz)
protein is responsible for engrailed
gene expression in cells & En is
repressed by high level of odd
skipped, runt or sloppy paired.The
Wg gene is transcribed in the
absence of eve & ftz genes.

17. Homeotic selector gene:
• These genes determine the identities
of segments by the end of cellular
blastoderm.
• Two major homeotic selector genes
are:
• 1. Antennapedia complex (ANT-
C):Control the development ofhead
and anterior thorax
• 2. Thorax complex (BX-C): Control the
development ofposterior thorax and
abdomen.

18. • Homeotic genes contain a
conserved DNA sequence of
180 base pairs.
• It is known as Homeobox.
• These sequence encodes
the 60 amino acid
homeodomain.These
recognize the specific DNA
sequence.

21. Bibliography :
• Breeding in insect by majnu yadav.
• Developmental biology by Gilbert (ninth edition)
• Zoological society (YouTube channel)
• Csir-net ,jrf life science(youtube channel)
• Re think biology (YouTube channel)
• SlideShare.net
• En.wikipedia .org

22. Thank you