Evolution and development
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Difference between vertebrate and arthropod (drosophila) body plan?
INVERTED drosophila- nerve cord on ventral side vertebrate- nerve cord on dorsal side
What signals are involved in specifying the dorso-ventral axis in drosophila- what are they homologues of?
DPP- patterns the dorsal side SOG- patterns the ventral side and it counteracted by DPP DPP- BMP, Sog- Chordin (In vertebrates BMP patterns the ventral side)
When do more specific characteristics of a group appear?
Occur later
How does diversity develop generally?
Through changes in control regions of control & target genes -Modifications of existing mechanisms-
What is the most important thing in driving evolution?
Changes in the timing and level of gene expression
Which 2 animals show where changes in hox expression have generated changes?
Pythons- loss of limbs- anterior expansion of hoxc6 and hoxc8 Butterfiles- changes in upstream regions of genes important for wing development- not repressed by Ubx in the haltere- 2 sets of wings
What are changes in time, place and level of expression important for?
Driving evolution- in comparison to changes in protein function
The change in level and duration of which gene formed the basis of evolution of beak size and shape?
BMP4
2 examples of developmental constraints
• Animals- maximum of 5 digits, pattern of humerus, ulna/radius and digits largely conserved • Blind cave fish
What is heterochrony- give an example
A change in the time/rate of developmental events Marsupial embryos- anterior limb is developed v quickly in comparison to mouse- allows embryo to crawl into pouch
What is neoteny- give an example
An animal reaches sexual maturity in a larval stage- before metamorphosis Axolotl