This document discusses pattern formation during embryogenesis. It begins by defining pattern formation as the development of spatial organization that establishes an organism's basic body plan and axes. Key genes that control pattern formation are homeotic genes, which regulate cell processes and contain a homeobox sequence. Hox genes pattern the anteroposterior axis by being expressed sequentially. In Drosophila melanogaster, cytoplasmic determinants, segmentation genes like gap and pair-rule genes, and homeotic genes work together to pattern each segment. Mutations in these pattern formation genes can lead to congenital malformations in humans and other organisms.

1. Presented by:
Nang Uttama Tungkhang
Roll no:20/BIOT/017
M.Sc 2nd semester,
Department of biotechnology
Mizoram university

2. • Introduction
 What is pattern formation
• Genes of pattern
formation
• Pattern formation in
Drosophila
melanogaster
• Medical conditions

3. INTRODUCTION
• What is pattern formation?
• The development of a spatial organization in which an
organism’s tissues and organs are all in their characteristic
places.
• Occurs during embryogenesis.
• Basic body plan is established.
• Major axes are established.
• studied most extensively in Drosophila melanogaster.

4. Genes of pattern formation
• Every organism has a unique body pattern
• This patterning is controlled and influenced by the
HOMEOTIC genes.
• These genes control and carry out tasks such as
 Cell division
 Cell migration
 Cell differentiation
 Cell death

5. • these are the master genes that regulates the
expression of numerous other genes.
• Homeotic genes contain a sequence of DNA known as
a homeobox, which encodes for 60 amino acids
within the homeotic transcription factor protein.
• If a mutation occurs in the homeobox of homeotic
genes, an organism will not develop correctly.
• these genes are found in many animals including fruit
flies, mice, and humans.

6. Hox genes
• Hox genes are responsible for
patterning along the antero-
posterior axis.
• The genes are expressed
sequentially beginning with the
paralogous group 1 , which is
expressed first.
• The sequential gene specify different
segment in cranio-caudal sequence
extending from paralogous group 1,
which specify the most cranial
structures, to paralogous group
13,which specifies the most caudal
structure.

8. Pattern formation genes in fruit fly
• Cytoplasmic determinants are present in the
unfertilized egg.
Provide positional information for placement
of axes prior to fertilization.
Establishes number and orientation of
segments
Ultimately trigger formation of specific
structures within each segment.
• Development occurs after fertilization.

9. Drosophila melanogaster
• Segmentation genes; directs the actual
formation segments after the embryo’s major
axes are defined.
• three sets of segmentation genes are
activated sequentially
 Gap genes
 Pair-rule genes
 Segment polarity genes

10. Drosophila melanogaster
• Gap genes –
map out basic subdivisions along the embryo’s
anterior-posterior axis.
• Pair- rule genes –
Define pattern in terms of pair of segments.
• Segment polarity genes-
Set the anterior-posterior axis of each
segments.

11. Drosophila melanogaster
• Homeotic genes
Specify the types of appendages and other
structures that each segment will form.
Encodes transcription factors.
 control the expression of genes responsible
for specific anatomical structures.
o Eg., ‘’antennae go here’’, ‘’legs go here’’.

12. Genetic disorders
Mutations in genes of pattern formation leads to
Lot of congenital malformations
Example :-
• Synpolydactyly; mutation in the HOX D13gene
A limb deformity: fusion of digits and production of
supernumery digits

13. Genetic disorders
• Aniridia; PAX6 gene mutation.
Partial or complete absence of iris.

14. Genetic disorders
• Antennapedia mutation in fruit fly;
Mutation in the antennapedia gene causes legs
to from the fly’s head.