Evo Devo

Question 1

Pharyngula stage

Answer 1

Embryos of vertebrates appear similar- developmental hourglass bottleneck

Still have morphological differences

Question 2

Modularity

Answer 2

One of two fundamental properties that dictate evolution if development

Development of anatomical units can be altered without affecting other organ systems

Also key feature of gene regulation- enhancers are modular

Question 3

Reuse

Answer 3

Use same molecules in different contexts means don’t have to evolve many different types

Molecular parsimony

One of two fundamental properties that dictate evolution if development

Question 4

Duplication degeneration complementation model

Answer 4

Force et al

A mutation can result in:
Nonfuctionalism
Subfuntionalism (partitioning of ancestral functions between two new copies)
Neofunctionalism

Seen in many gene families: Hox, globulin, collagen

Question 5

Paralogues

Answer 5

Duplicated genes

Question 6

Transcription factors bind to

Answer 6

Regulatory sequences

If this sequence in one copy mutates: pseudogene

Question 7

Hox genes

Answer 7

Encode TFs

Expressed in diff regions along the AP axis

Number and arrangement varies

Question 8

How many duplications in the whole Hox cluster in deuterostomes? Where?

Answer 8

Two

Once at the base of the chordates, again at the base of the teleosts

Question 9

Duplications in Hox genes led to

Answer 9

Subfunctionalism
Neofunctionalism

Different spatial expressions (e.g. Led to segmented body plan in Arthropods)

Thought to underlie Cambrian explosion

Question 10

Deep homology

Answer 10

When signal transduction pathways use the same proteins in the same order for the same function

Eg. Pax6 and eye development
Chordin/BMP4 and NS development

Question 11

Heterotypy

Answer 11

Mutation in protein coding sequence

Eg. Insects only have 6 legs because mutation in ultrabithorax inhibits distal-less

Corn mutation in Tga1 exposes corns

Mammals: sequence of Hox11 protein changed so that it associates with the Foxo TF- changes it from a repressor to an activator. Enables upregulation of prolactin, key in evolution of placental mammals

Question 12

Mutations in Hox cause

Answer 12

Changes downstream in the signal transduction pathway

Question 13

Heterotophy

Answer 13

Change in spatial expression of genes

Eg. Turtle changed where it expressed fgf10 to expand rib growth and form shell

Gremlin domain expansion inhibits apoptosis caused by BMP4 to produce webbed feet

Question 14

Heterometry

Answer 14

Change in the amount of gene product

Overexpression of shh in blind cavefish downregulates pax 6 so eyes don’t develop, increases jaw size and number of tastebuds

Changes in expression of BMP and calmodulin alter beak morphology in finches

Question 15

Allometry

Answer 15

Differential growth rates

Eg. Whales: Enormous growth of maxilla and premaxilla pushes over the frontal bone and forces nose to top to form blow hole, allows highly specialised jaw apparatus

Question 16

Heterochrony

Answer 16

Changes in timing of gene expression or a change in relative timing of developmental stages

Marsupials- more developed limbs

Neoteny: axolotl doesn’t undergo metamorphosis so still has gills. Controlled by thyroid hormone, can induce metamorphosis by injecting thyroid hormone

Question 17

Humans=neotenous apes?

Answer 17

Human head like juvenile chimp

Heterochrony in human brain as high growth rate continues after birth but doesn’t in chimps

Question 18

Developmental constraints on evolution

Answer 18

Physical
Morphogenetic (eg. Reaction diffusion mathematics)
Phyletic (needs restrict variety)