Presentation is loading. Please wait.

Presentation is loading. Please wait.

Drosophila homeotic mutants

Similar presentations

Presentation on theme: "Drosophila homeotic mutants"— Presentation transcript:

1 Drosophila homeotic mutants

2 Homeotic (Hox) gene complexes in Drosophila
lab pb Dfd Scr Antp Ubx abdA AbdB labial Deformed Antennapedia abdominal-A proboscipedia Sex combs reduced Ultrabithorax Abdominal-B Antennapedia Complex (ANT-C) Bithorax Complex (BX-C)

3 Expression patterns of homeotic genes in embryogenesis
labial Antennapedia Ultrabithorax abdominal A Abdominal B proboscipedia Deformed Sex combs reduced lab pb Dfd Scr Antp Ubx abdA AbdB

4 Two types of homeotic mutants in Drosophila
dominant mutations gain-of-function Transformations “anterior to posterior“ recessive mutations loss-of-function Transformations “posterior to anterior“

5 serially homologous limbs
Antennapedia - a homeotic mutant antennenal segments Arista coxa claw tarsal segments troch- anter tibia femur Antp / + antenna and leg are serially homologous limbs antenna transformed into leg

6 proboscipedia - transformation of mouthparts into legs
mx mx* lb lb*

7 Complex homeotic gene regulation
regulatory mutations Coding-region Bithorax Complex (BX-C)

8 Ubx is expressed in T3 and A1


10 Ultrabithorax binds DNA and regulates genes required for T3 and A1
Ultrabithorax expression Ubx protein OFF ON T2 specific gene OFF T3 specific gene ON A5 specific gene A1 specific gene

11 All abdominal segments take on a T2 identity if the bithorax complex is deleted
ubx abdA abdB triple mutant Wild type T2 T3 A1 T2 A8 T2

12 Antennapedia expression expands in flies mutant for the Bithorax complex genes
ANT-C BX-C Figures\Chapter09\DevBio7e09264.jpg

13 Ultrabithorax, AbdA, and AbdB normally repress expression
of the thorax-specific “leg gene” Distalless in the abdominal segments wild-type ubx abdA abdB triple mutant abdomen T1 T2 T3


15 Persistence of homeotic gene expression through development
Adult Imaginal discs larva embryo

16 Maintenance of homeotic gene expression
maintenance of transcriptionally inactive state maintenance of transcriptionally active state trithorax group (Trx-G) Polycomb group (Pc-G) extradenticle realisator gene Trx-G Pc-G transcriptionally open chromatin Dfd Exd pb Scr Antp closed

17 Lewis hypothesized that the duplication and diversification of homeotic master regulators underlies the evolution of an increasingly complex body plan

18 Distal-less gene Drosophila Precis (butterfly)
required for limb development Drosophila Precis (butterfly)

19 The human body is also built up from reiterated units (segments) with different identities along the A/P axis


21 Hox gene expression in mouse embryos

22 Mouse HOX gene expression patterns

23 Mouse hoxa3 and hoxd3 mutants
from Nature 370: (1994)

24 Wild-type mouse forelimb
hoxa-11 hoxd-11 Human hoxD13 mutation

Download ppt "Drosophila homeotic mutants"

Similar presentations

Ads by Google