W11L3 evolutionary developmental biology Flashcards
Some drosophila developmental mutants
-mutant bithorax (halteres develop as wing)
-mutant antennapedia (leg develop instead of antennae)
What is bicoid
-a homeodomain type transcription factor that is materially inherited as mRNA at the anterior end
Role of bicoid
-create a protein gradient in the AP axis
-Bicoid TF regulates expression of a gene ‘Hunchback’ (another TF)
-Multiple cis-regulatory sites are required for full expression of hunchback.
Even skipped (eve) regulation
- have an regulatory module for enhancer, consist of multiple binding site
- this control the expression of eve stripe at the location, help shape the segment boundary
The role of transcription factor in early development
- Early development genes contain cis-acting regulatory elements
- Their binding ability to transcription factors depending on gradient concentrations
- Some TFs repress expression, some promote expression
- This enables these ‘segmentation’ genes to be expressed in discrete regions
Hox genes
-hox gene regulated the identity of body part, conserved in many animal
-arrange in the way they are expressed in the AP axis
-The eight Hox proteins share a similar (180 bp) sequence. This suggests tandem duplications were involved with the origin of Hox genes
The hox gene paradox
-how does Hox gene that are extremely similar in sequence able to produce different animal bodies
explaination for hox gene paradox
-Coding divergence, gene duplication and downstream genes changes explain some of the variance
-change to gene and protein regulation mechanism have also been important
Hox gene in mouse
- The mouse genome contains 39 Hox genes
- Four Hox clusters arose through duplication in an ancestor
The effects of RNA processing on Hox gene expression
-differential translational efficiency of Hox mRNA
-Different hox protein is form (isoform)
-differential miRNA regulation
Why Co-option is a major mechanism in EvoDevo
Rather than build completely new genetic pathways from scratch, it is often “easier” for organisms to reuse existing systems in a new context
what is pannier
Pannier: a transcription factor that plays a role in dorsal cell fate during embryogenesis
Pannier intron and color variant
-Repeated inversions within a pannier intron drive diversification of intraspecific colour paIerns of ladybird beetles
-this lead to change in the location the gene is expressed at
-inversion may create new cis regulatory
mRNA splicing produces sex-specific dsx transcripts
Exon 1,2 and 3 code for transformer
-if there is the the 5th exon , create male
-if there is a fourth exon, create female
Papilio polytes characteristic
- Papilio polytes : with and without wing ‘tails’
- Female and males can look similar in some forms
- Other females are Batesian mimics – and resemble distantly related species
doublesex: mRNA splicing and protein evolution
-specific isoform were expressed in developing wings of female papilio
-Extensive levels of protein coding changes were observed between all mimetic forms
Co-option of sex determination gene doublesex(gene for sex determination) for mimicry
-diverse female mimicry have a single locus containing doublesex linked with all phenotype
-doublesex splice variation linked with phenotype
-causing protein coding change linked with phenotype
EvoDevo – can we apply the knowledge for beneficial application?
- CRSPR-Cas9 gene drive targeting doublesex cause complete population suppression in caged mosquitoes
XX doublesex mutants - develop with male characters
- cannot take blood meal
- cannot obtain energy
- cannot produce eggs
cis-regulatory vs. protein coding mutations
-Protein mutations in pigment transporters of island flycatchers cause striking phenotypic differences
-but regulatory mutations in bumblebee also cause striking phenotypic differences
why does mutation in cis regulatory region of gene are more likely to underlie most phenotypic evolution
-due to current understanding of gene regulation network, gene structure and fuction
-conservation in developmental gene (hard to mutate due to constrain)
Why are protein coding mutations
more common in the literature
-Parallel evolution among different species has helped identify protein coding variation
-all cause but polymorphic variation in the same gene, MC1R
The role of transposable elements in evolutionary developmental biology
- TEs can move to new positions within the same chromosome, or different chromosomes
- Originally identified in maize by Barbara McClintock
- Several classes: retrotransposons (copy and paste), DNA transposons (cut and paste)
pepper moth and TE
-TE insertion into the gene cortex causes melanism
-certain haplotype are only found in light/ dark moth
-During development cortex expression is higher in the dark carbonaria form than the light typica form
Cortex in other orgaism
-cortex modifies wing phenotypes in many butterflies and moths.
-Expression during development determines colour and cell morphology
