Hox genes Flashcards
What is homeosis?
Transformation of one body part to another.
What is a homeobox?
Conserved region of 180 nucleotides
What is the function of Hox genes?
Provide identity to segments
What is micro evolution?
Infinite number of changes of infinitely small size- constant selection of v. small changes.
What is macro evolution?
Cambrian explosion- took place in a long time but can’t have been many small changes. Had to be few big changes.
What are the two key genetic factors which determine evolution?
Circumventing pleiotropy and event frequency.
What types of genetic changes can there be which lead to evolution?
- Gene duplication and divergence: stays the same
- Protein sequence evolution: need a change to make a difference, frequent.
- Cis-regulatory sequence evolution: single nucleotide change leads to changes, frequent.
What is an example of cis-regulatory mechanism of a Hox gene and what is the gene?
Closely related flies have differences in trichomes on the T2 leg. D.virilis doesn’t have a naked valley. Ubx supresses trichome formation so causes the naked valley.
If you can find phenotypic differences in closely related organisms then you can track down the region that got changed.
What else can Hox genes regulate and give an example of that.
Can also regulate colouration. Separate cis-regulatory elements control yellow expression in the developing wing and body.
When did insects appear in the world?
Same time plants appeared on land. They had no wings.
Give an example of evolution of arthropods.
The brine shrimp Artemia has thoracic and abdominal limbs. It evolved to the fruit fly which has only thoracic limbs.
What gene promotes and what genes repress limbs in fly embryos?
Distalles promotes limbs.
Ubx and AbdA Hox proteins repress limbs.
How is limb repression controlled between different organisms?
Differences in C-terminal residues between fly and crustacean Ubx control whether limbs are repressed.
What mutations contributed to the evolution of hexapoda?
Serine to Alanine mutations in a regulatory domain.
