evolutionary developmental biology

Question 1

identification of hox genes as causal factors of homeotic transformations

Answer 1

hox genes are clustered on the same chromosome, the order of the genes mirrors the order of expression along the body axis
hox genes share a domain of 60 amino acids which bind to dna

Question 2

how are hox genes expressed

Answer 2

vertebrates have 4 hox clusters due to 2 rounds of whole genome duplication
they are expressed in a collinear fashion
vertebrate hox genes also determine axial segmentation identity

Question 3

what are homologues and analogues

Answer 3

homologues = characters in different organisms inherited from a common ancestor
analogues = characters in different organisms similar in shape or function not due to a common ancestor

Question 4

what are keys to finding homologues

Answer 4

gene expression patterns
problem with pleiotropy = genes expressed in many unrelated places
phylogenetic relationship is crucial

Question 5

what are hox genes used in almosrt all animals for

Answer 5

anterior to posterior body axis patterning

Question 6

classical view on eye evolution

Answer 6

existence of different types of eyes in various lineages of animals were considered to be a classical examples of convergent evolution
pax6/eyeless and other transcription factors are necessary for development of both insects compound eyes and vertebrate lens eyes
the discovery of a common regulatory network for eye development suggests the presence of proto-eyes in the common ancestor from which various eyes evolved

Question 7

what are common toolkit genes

Answer 7

genes necessary for animal development

found through resolution of phylogeny using molecular information

Question 8

how has the vertebrate jaw evolved

Answer 8

the jaw is an evolutionary novelty of Gnasthostomes
jaw is a modified gill
heterotopic shift of epithelial cells induce expression of patterning genes in mesenchymal interaction implicated in the evolution of jaws
GF secreted by epithelial cells induce expression of patterning genes in mesenchymal cells

Question 9

how has arthropod appendages evolved

Answer 9

different groups of arthropods have different appendage organisations
insects have no appendage in the abdominal region
insects and crustaceans have different appendage organisations but have the same pattern of Hox gene expression
drosophila Ubx sequence suppresses appendage formation whilst artemia Ubx does not
the evolutions of Ubx function underlies the difference in appendage organisation