Evo-devo 2

Question 1

Dog Evolution factors:

Answer 1

• reproductive separation and limited effective population sizes of established breeds provide extensive opportunity for divergence - genetic drift
• breeds are also under selection for a variety or morphological and behavioural traits - adaptive
• cranial variation with functional consequences, such as breathing

Question 2

Modularity

Answer 2

• identified as independence amoung groups of phenotypic traits
• can help organisms avoid trade-offs and likely alters the rate and direction of evolution-modularity may predispose dogs for rapid evolution of jaw length

Question 3

BMP

Answer 3

Bone morphogenetic protein

-have known role in craniofacial development

Question 4

Morpholinos

Answer 4

molecules we can design to block the activity of specific genes

Question 5

Zebrafish (danio rerio)

Answer 5

• model organism for genetic manipulation
• Injection of BMP3 morpholino at the one-cell stage
• Knocks down the function of BMP3 throughout development

Question 6

Loss or reduction of BMP3 function causes..

Answer 6

• shorter flatter face
• BMP3 is the reason why pugs, bulldogs, are brachycephalic
• also shows that the effect of BMP3 in a fish is similar to that in a dog - conserved toolkit gene

Question 7

Summary

Answer 7

• Divergence among dog breeds appears to be due to standing variation from their common grey wolf ancestors
• The main change in dog skulls involves lengthening and shortening of the jaws
• Modules in the skull may contribute to the evolution of these changes in jaw length by circumventing tradeoffs
• Jaw length in dogs seems fairly simple, being largely explained by five regions of the genome
• BMP3 looks to be especially important for determining jaw length (alleles are fixed between dolichocephalic and brachycephalic breeds, and it effects zebrafish jaw length)