Hox genes Flashcards
What are homologs?
Molecules or features that have resulted from common ancestry
What are orthologs?
The same molecule or feature in different organisms, results from homology across different species
What are paralogs?
A shared sequence in the same species that diverged into a gene family
When did Hox genes appear?
The Cambrian explosion
How do we know that Hox genes are an ancestral trait?
They allow for bilateral symmetry since they help establish the anterior-posterior and left-right axes
How many Hox genes are in Drosophila? How many chromosomes are they on?
8 genes on one chromosome
How many Hox genes are in vertebrates? How many chromosomes are they on?
> 8 genes on 4 chromosomes
Why do vertebrates have more Hox genes that are more spread out than flies?
The duplication occurred more in vertebrates than it did in flies
What is the homeobox?
A 180 bp region that encodes a distinct 60 amino acid sequence that will fold into the homeodomain
What does the homeodomain do?
Allows binding to DNA to allow Hox genes to be transcription factors
What are the two features of Hox genes?
They have the homeobox and regulate development of the entire body plan
Why are all Hox genes paralogs?
They all came from one ancestral gene that duplicated itself
How are the Hox genes placed on the chromosomes?
The genes that are expressed in the anterior end are on the 3’ end of the chromosome and the genes expressed in the posterior end are on the 5’ end
What are the 4 steps in a gene cascade?
- Selectors
- Regulators
- Realisation
- Process/function
