Evo Devo Flashcards
Ernst Haeckel
tied similarities between various animal embryos and development pathways critical to establishing homology to evolutionary change
Ontogeny recapitulates phylogeny
single celled zygote –> jelly fish like gastrula –> wormlike embryo –> fish like embryo –> tadpole like embryo –> tetrapod fetus
Master gene
Genes that control where, when, and how other genes are expressed
- make proteins that signal, activate, mark, or otherwise communicate with other genes and their products
- often sequentially expressed in a set pattern
- also called homeotic(HOX) or developmental regulatory genes
Homeotic Genes
genes regulate where, when, and how genes downstream will be expressed
expression of body parts –> “antennapedia” is the most famous
highly conserved and often occurring in a multi-gene families (result of ancestral duplications?)
HOX gene expression
set up anterior/posterior and dorsal/ventral in insects
anterior is the front towards the head, posterior is the back towards the butt
dorsal is the top side and ventral is the bottom side
Gene duplication
most important source of new genes
misalignment in meiosis leads to unequal crossing over (one chromosome gets extra copies of a gene)
consequences gene duplication
“new” copy may not have same functional constraints as ancestral copy
mutations may accumulate in new copy with fewer consequences
mutations may allow daughter to perform new functions
may help or hurt…
Gene families
cluster of genes similar in structure and sequence
ex. HOX genes
Globin Genes
example of a gene family
similar in structure –> repeated sequence motifs that allow us to recognize them as similar
different genes expressed at different times in development –> genes can be “turned on/off”
each gene product is slightly different (ex. fetal product has higher affinity for oxygen)
selection acts independently on each gene
Complex change
Can come from very simple basis
Conservation of HOX genes
anterior-posterior axis
co-linear on chromosomes
what do master genes also specify?
master genes also specify similar kinds of structures
eye development spurred by PAX genes –> even though eyes form differently, all initiated by similar genes
difference between evolutionary theory and evo-devo
classical evolutionary theory looks at survival of the fittest
evo-devo looks at the ARRIVAL of the fittest
what is polyploidy?
more copies of ALL genes
what are pseudogenes?
non-functional genes that are still included in a gene family
usually not transcribed
may eventually evolve new function or role through changes in sequence or in transcription pattern
