L17 - Genome Evolution Flashcards
Within orgaisms most of the genes are ___________ what changes is the __________
The same
Expression of the genes
What is phylogeny
Systematic classification of the animals into groups based upon their morphology
When genome sequencing was first used what was seen
That most of the genes are the same
From a phylogenic tree what needed to be estimated
The timing of the branch points
Why do we share manyg many genes with other species
Many genes arose at the common single cell stage which were the requirements for life
What is the traditional way of calibrating the clock
Using fossil records and carbon dating
What is the change in the nucleotide sequence change between humans and organutans
1.5 bases per 100
FOXP2 differs in mouse, chimp and humans at which three positions
80, 303, 325
In FOXP2 at position 80 was is the AA in humans and in mice
D in humans and chimps
E in mouse
So the common ancestor of human and chimp …
Had a D at psotion 80
Parsimony means
Assuming the simplest model
How is the parsimony decided
Programs related to blast consider all of the possible scenarios to come up with the most likely one
If 80D had arrisen twice by chance - what would this have been an example of
Convergent evolution
Molecular phylogeny is compared with ….. to give us a deeper understanding of evolution
Morphological phylogeny and fossil records to give us a deeper understanding of evolution
How many vertebrate FGFs are there?
How many clusters?
22
4
What is special regarding the composition of FGF in the ciona
What does this suggest
It has a single representative of each of the 4 clusters
Suggests common ancestory of Ci and vertebrates had 4 FGFs
What are the two ways in which so many FGFs arise
Changes in ploidy of the cells and local duplications
New copies of genes in the genome are known as …
Paralogues
What is special about the large strawberry
It is octaploid
After duplication it is likely that the duplicate genes will first be ….
REDUNDANT
The extra copy of the gene would the be able to ….
Change in the following ways
Change pattern of expression OR change in strucutre of the protein
What are thought to be the most common sort of change which drives morphological evolution of animals
Changes in expression patterns
Does evolution involve the creation of new genes
No it is the modifcation of old ones
IT IS GENE EVOLUTION WHICH DRIVES MORPHOLOGICAL EVOLUTION
Why are changes in expression patters thought to play a major role in morphological evolution
Because enhnacers can change easily
Why are enhancers able to change easily
Due to the fact that the exact psoiton of an enhancer is unimportant and TF bidning site motifs are simple
Why do changes that affect the STRUCTURE of a protein have to be more precise
So as not to introduce a stop codon, change the ORF, interfere with folding or disrupt splicing
How does chick and mouse show evidence of change of expression playing a major role in evolution
Chick has a longer neck - more cervical vertebrae and less thoracic vertebrae
What hox gene specifies the cervical vertebrae
Hox C5
What hox gene specifies the thoracic vertebrae
Hox C6
What can be said about the expression of HOX C6 in the chick compared to the mouse
Expression of C6 (specifies the thoracic vertebrae) starts more posteriorly in the chick
Genes that a capable of the formation of organs are known as
Master regulatory genes
What occurs when a master regulatory gene is ectopically expressed
Ectopic limb/organ development
Are ectopic organs functional?
What is this an example of?
Yes functional
Evolutional robustness
Which organism has legs on their abdomens
Crrustaceans or insects?
Crustaceans have legs on their abdomens but insects dont
What does Dlx specifiy
Leg precurrsor cells
Describe the expression in fly embryos
Ubx expressed in abdomen where it represses Dlx ==> no legs in abdomen
What does dlx stand for
Distal-less
Explain the expression of Ubx in insects - what does this imply about the evolution of Ubx
Dlx and ubx BOTH expressed in the abdomen
Crustacaen ubx has an antirepression motif which was lost in insects
