Topic 8 - Generating Diversity Flashcards
What are somites?
Paired segmented structures formed as a result of changes along the anterior–posterior axis of the mesoderm, which give rise to the vertebrae, muscles and other tissues.
What is neurulation?
The developmental stage during which the neural plate invaginates and rolls into a tube to form the neural tube; the forerunner of the spinal cord and brain.
What are rhombomeres (neural development)?
Distinct regions in the developing hindbrain. The cells in different rhombomeres go on to differentiate into neurons that will innervate different targets (such as different muscles of the face).
What are homeotic transformations?
Changes in the identity of an entire body segment, such as transforming a leg-bearing segment into a wing-bearing segment.
What are hox genes?
Hox genes (a subset of homeotic genes) are a group of related genes that control the body plan of an embryo along the cranio-caudal (head-tail) axis.
What are the defining properties of hox genes?
Their protein product is a transcription factor.
They contain a DNA sequence known as the homeobox
In many animals, the organization of the Hox genes in the chromosome is the same as the order of their expression along the anterior-posterior axis of the developing animal, and are thus said to display colinearity.[2]
What is the term used to describe genes within the same species that have arisen from a common ancestor through a duplication event?
They are paralogues.
What is hox gene colinearity?
The observation that the 3′ to 5′ order in which Hox genes are located along their chromosomes mirrors the anterior–posterior order in which they are expressed in the body.
What is the term used to describe genes within the same species that have arisen from a common ancestor through a duplication event?
They are paralogues.
What is hox gene colinearity?
The observation that the 3′ to 5′ order in which Hox genes are located along their chromosomes mirrors the anterior–posterior order in which they are expressed in the body.
Overall, evolutionary differences in the number of vertebrae and their individual morphologies can therefore be attributed to at least two mechanisms. What are they?
alterations in the number and size of somites, via changes in the segmentation clock (frequency of oscillations, or overall number of oscillations)
mutational changes in Hox genes, or their downstream targets, that redefine the structures that each somite can produce.
