Spatio-temoral Collinearity Flashcards
Who founded the principle of collinearity? When?
Edward Lewis, 1957
Which species did Lewis study?
Drosophila melanogaster
What is principle of collinearity?
Genes arranged on the chromosome in the same order as their corresponding body segments
eg. First set controls head and thorax
Which genes are a good example of Collinearity?
HOX
What direction are HOX genes numbered?
3’ to 5’, starting at telomeric end
Eg. HOX1, HOX2, HOX3
When is Spatial Collinearity most pronounced?
In vertebrates where two other forms of Collinearity are present
Another form of Collinearity?
Quantitative Collinearity - expression of the posterior most gene in a cluster is the strongest
Which animals have compact HOX gene clusters?
Vertebrates
What is the main factor that causes tight gene clustering?
TEMPORAL Collinearity
Which species has unusual collinearity? Why?
Sea urchins
Their ROTATIONAL SYMMETRY causes an unusual gene order in HOX clusters
What are HOX genes? (2)
Group of related genes that specify body regions along anterior-posterior axis
In verts, HOX genes specify the TYPE + SHAPE OF VERTEBRAE
Where are HOX genes located in vertebrates?
Very close to one another in clusters on the chromosome
HOX genes function? (3)
Orientate the embryo
- Specify characteristics of ‘position’
- Ensure correct structures form in correct places
What do analyses of animal genomes support?
The idea that HOX gene clustering is essential for coordinating the times of different gene activations
How many HOX genes and HOX gene clusters do humans have?
39 HOX genes
Organised into 4 gene clusters
