Animal development 6 Flashcards
What is a paralogue?
A pair of genes that derives from the same ancestral gene and now reside at different locations within the same genome
What is an orthologue?
Genes that are found in different species that evolved from a common ancestral gene by speciation
Describe the process of gastrulation in amphibians
Cells move inwards forming the dorsal blastopore lip
Cells of the animal pole spread out pushing the surface cells below them towards and across the dorsal lip
These cells curl inwards into the interior of the embryo where they from the endoderm and mesoderm
What is neurulation?
The folding process in vertebrate embryos, which includes the transformation of the neural plate into the neural tube
The embryo at this stage is termed the neurula
The cells migrate from the roof of the archenteron
What is embryonic induction?
The embryonic process in which one group of cells, the inducing tissue, directs the development of another group of cells, the responding tissue
What cell layers are involved in embryonic induction?
The mesoderm will cause the ectoderm to form the neurectoderm
What is the grey crescent?
The future dorsal, or back, side of the embryo
What happens if the grey crescent is not present?
No dorsal structures develop such as the nervous system, notochord, etc.
What is determination?
A stable change in the internal state of a cell such that its fate is now fixed
What is the primary embryonic induction?
The induction of a body axis
What is an organiser?
A signalling centre that directs the development of the whole embryo or part of an embryo
What is the Spemann-Mangold organiser?
A group of cells that are responsible for the induction of the neural tissues during development in amphibian embryos
How does the Spemann-Mangold organiser form?
A β-catenin gradient is formed after being initially synthesised throughout the embryo from maternal mRNA
The gradient is formed by an interaction between Dsh and GSK-3 proteins
Dsh protein is initially present in the vegetal pole
After fertilisation, Dsh is transported by microtubules laterally along the cortical cytoplasm to the future dorsal region (grey crescent)
GSK-3 normally degrades β-catenin but Dsh blocks GSK-3 in the future dorsal region
Thus the future dorsal nuclei receive β-catenin but the future ventral ones do not
The induction of the organiser is then signalled by cells in the Nieuwkoop centre where β-catenin and TGF-β proteins overlap
Describe the gene regulatory network that leads to the dorsal lip organiser being formed?
The siamois gene is normally repressed by the Tcf-3 transcription factor in the future ventral half
β-catenin activates the expression of the siamois gene in the future dorsal half
The siamois protein interacts with TGF-3 proteins to control goosecoid transcription
Goosecoid protein then activates genes in the dorsal lip organiser
What does BMP4 do?
Inhibits cells from forming neural tissues
It is expressed in the future ventral half of the embryo during gastrulation and promotes the formation of ventral structures
