L15 Hox and evodevo Flashcards
What was thought to make us different morphologically?
Much of what makes us different (morphologically) is thought to be caused by changes in expression of a common set of developmental genes.
What method is used to determine similarity in proteins?
BLAST protein alignment.
What is the procedure of BLAST?
- Input the amino acid sequence of the protein in question (query).
- The Blast program searches huge databases for other proteins which have similar sequences.
- Then it shows an alignment of a query protein to a protein called zen (subject)
What does similarity between protein sequence suggests?
Similarity found between protein sequence suggests that the proteins evolved from the same common ancestor and that the proteins have similar molecular functions.
How many vertebrate FGFs are there?
There are 22 vertebrate FGFs that fall into 4 clusters based upon protein sequence alignment.
What is Ciona?
Ciona (a chordate) has single representatives in each of the 4 groups (in red). This suggests that the common ancestor of the sea squirt and vertebrates had 4 FGFs
In what ways does the extra copy duplicated can change?
The extra copy can change in the following ways:
1) pattern of expression during development
2) structure of the protein. Both small changes caused by point mutations and big changes caused by domain swapping.
This is gene neofunctionalisation
Why are changes in expression patterns of genes thought to play a major role in evolution?
Because regulatory elements can change easily.
Accidents during meiosis could bring a new enhancer close to the gene.
Is the exact position of an enhancer important, explain?
The exact position of an enhancer is usually unimportant, and the DNA sequence for transcription factor binding sites is simple. Thus, it should be relatively easy to add or delete sites by rearrangements, insertions, deletions or base pair substitution.
Changes that effect protein structure would have to be more precise so as not to introduce a stop, change the reading frame, interfere with the protein’s folding or disrupt RNA splicing.
What are Hox genes?
Hox genes are transcription factors that are found in clusters in the genome
What are the features of hox genes?
- They all have sequence similarity suggesting that they originated from one gene
- They are expressed in specific segments in the embryo
- Changing hox gene expression(in the embryo) results in changes in segmental identity.
What may explain the loss of limbs during snake evolution?
Shifts in Hox gene expression.
Expansion of HoxC6 and HoxC8 expression could confer many of the morphological changes (shift towards thoracic) seen during the evolution of snakes
Crustaceans have legs on their abdomens but insects don’t, why?
It turns out that this may be because of changes in the protein sequence.
What gene evolution explains why insects don’t have legs on their abdomen?
- ubx evolution may explain why insects don’t have legs on their abdomen.
- In fly larvae, the Dlx transcription factor specifies leg precursor cells.
Ubx is expressed in the abdomen where it represses Dlx expression.
What are the features of the Ubx gene in crustaceans?
Ubx is expressed in the abdomen of crustacean larvae, but it doesn’t turn of dlx expression.
It is thought that the Ubx gene became able to repress Dlx expression (changes made in the protein sequence) in an ancestor of Drosophila.
