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Comparing Eye Development in Flies & Vertebrates: Role of Pax6 & Hox Genes, Slides of Life Sciences

An in-depth analysis of the evolutionary conservation of eye development patterns in flies and mice, focusing on the roles of pax6 genes and hox genes. Topics covered include the evolutionary conservation of neural induction, patterning of the neuroectoderm, and sequential formation of photoreceptor clusters. The document also explores the arguments for and against the idea that eyeless/pax6 is a master gene for eye development.

Typology: Slides

2012/2013

Uploaded on 08/30/2013

faroq
faroq 🇮🇳

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Download Comparing Eye Development in Flies & Vertebrates: Role of Pax6 & Hox Genes and more Slides Life Sciences in PDF only on Docsity!

Eye

Claw

2nd Axis

Evolutionary Conservation of Hox Expression Patterns

Drosophila

Neuroectoderm

Mouse Neural Tube

Sonic Hh

BMPs

Msx

Nkx2.

Gsh

Dorsal

Dpp

ind

msh

vnd

dpp

Patterning the Neuroectoderm in Flies and Mice

A P

Hh

Dpp

Hh

Hh BMP-

A

P

Fly wing disc

A/PAxis

Vertebrate Limb Bud

D/VAxis

P/DAxis

D V

A P

NotchSignaling

A

P

D V

NotchSignaling

D V

A P

Distalless

A

P

D

V

Distalless

A

P

Specification of the

eye disc in the embryo

1,000-X growth

eyeless

A master eye gene?

Eye Primordium20-40 Cells

Furrow

A

P

Growth and patterning of eye imaginal disc in larvae

dpp

hh

Early Steps in Fly Eye Development

R

8

R

7

Sequential formation ofphotoreceptor clusters Furrow

R^2 R^5

R 3 R 4

R 8

R^1 R^6

R^78

7

3

5

Photoreceptor Development^1

Fly Eye Development

Furrow

A

P

Patterning of theeye imaginal disc

dpp

hh

docsity.com

Opticnerves

Lens

Photoreceptors

Epidermis

Invaginating eyeimaginal disc Eyedisc

Morphogenetic furrow Ant.

Post.

8 7

3

5

PhotoreceptorDevelopment 1

Photoreceptorsinduce lens cells

Furrow

OpticVesicle

Brain

Lens

Retina

Cornea

Opticnerve

Photoreceptors

Iris

Future lens F u tu re retin a

Brain Futurelens Futureretina

Iris

CorneaLens Retina

Opticnerve

Photoreceptors

Iris fold

Lens

Cornealfold

Lens fold

Eye primordium

Migrating lens cells

Future Retina

Comparative Eye Development

Fly

Vertebrate

Squid

Is Eyeless/Pax6 a Master Gene for Eye Development?

Arguments in Favor:

Wild-type Wing

Decreased activity of

pax

genes results in reduced eye size in flies,

mice, and humans.

pax

genes are expressed in the early eye primordia of flies, humans,

and squid, in which eyes were thought to have evolved independently.

Wing Mis-expressing Human

pax

gene

Eye

3) Mis-expression of fly or human pax6 genes in certain fly tissues (e.g.

wing) result in formation of ectopic eyes.

Hox genes

A/P Axis

Abdomen

Head

Tail

Mouth

Anus/ Genitals

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Sog/Chd Dpp/BMP

Non-neural Ectoderm^ Neural Ectoderm

D/V Axis

Photosensitive organs

Sensory Appendages?

Eyespot?

Gills?

Protrusions or appendages

Reconstructing the Common Ancestor of Flies and Humans

What Was So Great About Our the Common Ancestor?

The common ancestor of humans and flies must havelived in a complex eco-system with many other species,some of which ate it and others of which it ate.

The creature and its decedents somehow displaced allother animal forms.

Why?? What was so great about this animal??

The Question: Possible Answers:

The ancestor evolved a mechanism for extracting low levelsof oxygen from the atmosphere and delivering them tointernal tissues.

The ancestor evolved HOX genes, which allowed for thesubsequent diversification of individual body parts.