Evo-Devo and Gene Expression

Evo-devo

Comparative study of organismal development and how it evolved

Major evo-devo finding

Most animals share a common set of genes

Genetic toolkit

Highly conserved genes (nearly all animals) that regulate morphological development

Homeotic genes

Subset of the toolkit that direct development of body segments or structures

Hox genes

Most animal homeotic genes. Transcription factors giving front-to-back positional info

Homologous genes

Genes in different species inherited from a common ancestor

How Hox genes evolved

Gene duplication, whole cluster duplication, gene loss

Ubx in Drosophila

Codes for hind legs. The homologous gene is expressed in mouse hind legs

Sea spider abdA example

abdA is missing, so sea spiders lack an abdomen

Heterometry

Different amount of gene expression (e.g., Bmp2 higher in bat forelimbs)

Heterochrony

Different timing of expression (e.g., giraffe neck bone growth stop signal is delayed; still 7 vertebrae)

Heterotopy

Different location of expression (e.g., duck vs. chicken feet; limb gene expressed in the tail)