EvoDevo Flashcards
Which anatomical features are shared in vertebrates?
pharyngeal arches dorsally located nervous system segmented trunk muscles vertebrae complex head with sensory organs
What is the relationship between:
a) human arm, seal limb, bird wing and bat wing?
b) bird wing and bat wing?
a) all developed from a common tetrapod andestor = are homologous
b) evolved independently from each other = are analogous
What is a developmental hourglass model?
predicts an hourglass-like divergence during animal embryogenesis:
- embryos more divergent at the earliest and latest stages
- conserved during a mid-embryonic (phylotypic) period
= source of the basic body plan for animals within a phylum
Why is there the biggest diversity in the eary embryogenesis and in the pharyngula stage (talking about hourglass model)?
beginning: signal gradients induce activity throughout the gastrula
- Hox genes
- environmental and developmental constraints
- developmental burden
- random chance
end (pharyngula stage): a lot of local inductive interactions that are confined to their own modules and allow possible modifications
Gene regulatory networks can be of different hierarchies. In which 4 boxes do we divide them?
Box I: establish broad domains that regionaize the organism with respect to major body axes
Box II: define progenitor fields within the body parts
Box III: define identity and spatial boundaries of body parts
Box IV: terminal cell fate specification
–> differentiation gene batteries
What is a developmental genetic toolkit?
a set of a few 100 genes that are involved in 3 key processes:
- cell differentiation (Hox)
- cell-cell communication (Wnt)
- cell adhesion
conserved ones can be exchanged from one animal group to another
e.g. Pax6 -> eyes in mice and Drosophila even tho not homologous structures and even ectopically
Which properties allow for generation of morphological diversity?
- evolvability (size vs number of vertebrae)
- modularity
- cis-regulatory mutations (in enhancers)
- duplications and sub-functionalizations
- structural mutations (in coding regions, following duplications)
What are
a) enhancers?
b) cis-regulatory elements?
a) sequence modules that contain binding motifs for transcription factors
b) genomic regions containing the enhancers
Around mammalian developmental genes, regulatory landscapes can be very big (up tu 1Mb or more). Which event in mamm. evolution allowed de novo evolution of enhancers and diversification of their use?
2 rounds of genome replication
What is
a) heterotopy?
b) heterochrony?
a) evolutionary change in the spatial arrangement of an animal’s embryonic development
b) a change to the rate or timing of a development process
How can cis-regulatory networks be identified and compared between species?
- identification of enhancers by searching for conserved sequences
- identification of active enhancers and promoters by ChIP-Seq
What is Chip-Seq?
chromatin immune precipitation and sequencing
- cross-link protein to DNA
- shear DNA strands (sonication)
- immunoprecipitate target protein by bead-attached-antibodies
- unlink protein & purify DNA
- sequence DNA
- map to genome
Which histone marks mark
a) active enhancers?
b) active promoters?
a) H3K27ac
b) H3K4me3
What are possible cis-regulatory mutations?
- loss of TF binding sites in CREs
- insertions/deletions between TF binding sites in CREs
- recruitment of transposable elements as new CREs
- recruitment of new TF to mutations in CREs
Describe an example for a loss of TF binding site in CRE.
Pitx1 = can bind to hindlimb enhancer, if present
- present in marine stickleback
- absent in freshwater stickleback
