Genome Evolution Flashcards
For great apes and man how frequent were changes in nucleotide sequence?
1% per every 10 million years
How can we estimate the rate of sequence change?
By completing the fossil record to genomic data
When we assemble the tree which model do we tend to pick?
The simplest one
Describe the differences in FOXP2 in mice, chimp and humans and what conclusions can be drawn from this
There are differences in the amino acids at 80 and 303
Since mice and chimp have 303 T it is likely their common ancestors also did (humans = 303 N)
Chimps and humans had 80D so it is likely that their common ancestors also did ( mice = 80E)
This accomplishes a tree with two changes
What is parismony?
Assumption of the simplest model
What is convergent evolution?
Convergent evolution is the process by which unrelated or distantly related organisms evolve similar body forms, coloration, organs, and adaptations
It is not common but does occur
How many vertebrate FGFs are there and how many clusters do they fall in to?
22 which fall unto four clusters based upon their protein sequence alignment
What does the organsims ciona suggest about FGFs and why?
It suggests that common ancestor of the sea squirt and vertebrates had four FGFs as it has a representative FGF from each cluster
How may have so many FGFs arised?
Gene duplication - changes in ploidy and local duplications
What is a paralogue?
A new copy of a gene which arises in the genome
What is a syntelog?
a special case of gene homology where sets of genes are derived from the same ancestral genomic region. This may arise from speciation events, or through whole or partial genome duplication events (e.g. polyploidy)
An extra copy of a chromosomal region can change in what ways?
1) Pattern of expression
2) Strucural in the protein. Both small changes caused by point mutations and big changes are caused by domain swapping
What is thought to be the most common driving force in the morphological evolution of animals?
Changes in gene expression
Why are changes in expression patterns of genes though to play a major role in morphological evolution?
Because enhancers can change easily
How could non homologous recombination affect an enhancer?
It could bring a new enhancer closer to a gene
Why are changes in enhancers ore likely to affect evolution than changes to a protein?
Enhancers; exact position is not usually important and the DNA for TF binding sights is simple so it is easy to add or delete sites by rearrangements, insertions, deletions or BP substitutions
Proteins; changes have to be precise so as not to introduce stop codons, change the reading frame, interfere with folding or disrupt splicing
Changes in reguatory genes can correlate to what type of change?
Morphological
Give an example between mice and chicks where regulatory changes affect morphology
C6 - in the chick expression starts more posteriorly correlating with a longer neck and fewer thoracic vertebrae compared to a mouse
How can we show that regulatory genes are responsible for large evolutionary changes in model organisms?
By changing gene expression, creating ectopic organs
What is a master regulatory gene?
A gene on top of a heirarchy capable of big tasks such as setting up organs. They regulate whole gene networks
Why might crustaceans have legs on their abdomen but insects do not?
Changes in the leg master regulatory gene during evolution
Ubx evolution can be used to explain what?
Why insects do not have legs on their abdomen
Describe the expression of Dlx and Ubx in flies and their roles
Dlx = leg precursor cells
Ubx is expressed in the abdomen where it represses Dlx
As a result legs form only in the thorax of the fly
There are six spots of Dlx expression in the fly
Is ubx expressed in the abdomen of crustaceans?
Yes it is
It is also expressed in the thorax so researchers have concluded that crustacean ubx does not act as a repressor
How is crustacean and insect Ubx different?
Crustacean has an antirepression motif which has been lost in insects
Describe the results of the experiment which shows the difference between crustacean and insect ubx
Crustacean Ubx expressed in the thorax of flies does not repress Dlx, however drosophila Ubx does repress it
