Midterm 2 - Notes 3 (Part 1) Flashcards
What is molecular evolution mediated by?
Transposons
- but doesnt have to be
What are 4 major models of genetic innovations?
- Intragenic mutation
- Gene duplication
- DNA segment shuffling
- Horizontal transfer
What is the most common model for genetic innovations?
Intragenic mutations
Where do intragenic mutations occur?
Within protein coding regions
What happens with intragentic mutations?
Slightly changes the codon and possibly changes the function
- this occurs gradually
What is gene duplication?
Creates a 2nd copy that can be identical to the original gene in the genome
What does gene duplication allow?
Allows one copy to evolve while maintains the original function at the same time
What is DNA segment shuffling?
Mixing 2 parts of a genes in order to create a new gene
- contains parts of old genes in recombination
What is vertical transfer?
Transfer from one generation to the next in the same genome
- this is a slow process
What is horizontal transfer?
Transfer from one genome to another
- this is a rapid process
- novel function from distinct transfer
Exon shuffling
Is an evolutionary process for creating new genes form pre-existing ones by recombination between introns of 2 separated genes or by transposition of mobile DNA elements
Where are TE located via transposition of 2 integrated DNA transposons?
On either side of the gene (that wants to be cut out)
- this is for translocation or duplication
- its on either side the the exon for exon shuffling
What are cis elements needed for?
Expression and processing
What is transposition of a retrotransposon mediated by?
RNA transposon
Where are TEs located via transposition of a retrotransposon? (2)
- Upstream of the gene
- gene duplication - In an intron
- exon shuffling
What does retrotransposons involve?
Run through transcription but utilizing the poly A signal on the TE
What may or may not be included with retrotransposons?
Cis regulatory elements
What does homologous recombination between TE not involve?
Transposition
- can use any type of TE
What does homologous recombination between TE need?
TE
Where are the 2 pairs of TEs of the same type located on 2 different genomic location?
- On either side of the gene
- gene translocation - On either side of introns
- exon shuffling
What does homologous recombination between TE involve?
Double cross over between identical TE sequences
What is the problem in homologous recombination between TE?
The segments are very similar
What do most proteins contain?
Multiple domains
What can domain shuffling via transposons do?
Combine exons from distinct proteins
- can have a drastic effect on the new types of proteins
What can combinations create?
New functions
EGF
Epidermal growth factor
What does an EGF initiate?
Signalling cascade
- binds to a receptor
What does chymotrypsin do?
Its a protease (for digestion)
- it cleaves peptide bonds
- unspecific
What does urokinase do?
It is a plasminogen activator
- it cleaves plasminogen and activates the formation of blood clods
What does Factor IX(9) do?
It cleaves factor X(10)
- allows blood clod generation
What does plasminogen do?
It cleaves fibrin
- it dissolves blood clods
- protein protein interaction domain
What are retro-copies?
Copies of regular genes
- via transposition of “normal” cellular gene transcripts
What may RT of non-LTR transposons act on?
May act on any RNA with a poly A tail
- binds and acts on a regular mRNA on the cell and brings it back into the cell and preforms RT and brings it into the genome
What do retropsons (retro-copies) differ from?
Other gene duplicates
- direct repeats and a poly A tail remainder
- no introns because they would have been spliced out during RNA processing
- no regulatory elements duplicated because they occur further upstream so they are not part of the duplication site and get a different expression pattern than the parent
What are retro-copies prone to become? (2)
- Processed pseudogene
2. Neo-functionalization
What are 4 things that are needed in order to become successful is a retro-copy?
- Needs to be inserted completely
- needs to have a complete genome
- needs to be downstream of the promoter so it gets duplcicated - Must originate from a gene expressed
- expressed in the germ line - Must gain regulatory elements
- needs a promoter and a terminator - New regulatory modules must be advantageous
- need an adaptive advantage to be able to be maintained
Pseudogene
A section of a chromosome that is an imperfect copy of a functional gene
- evolves neutrally
