Introduction to the main cellular components of development Flashcards
Origins of developmental biology
- Aristotle was amongst the first to think about development nearly 2 and a half millennia ago
- Thought that the organism was in the head of the sperm whether that be a human or a dog etc.
A frog’s life
The stages through through fertilisation to hatching is called what?
embryo genesis
What is development controlled through?
Development is controlled through a number of different regions of the embryo called organizers
What are you no longer considered an embryo?
What continues to still happen?
Beyond hatching development still progresses
Once out of egg you are no longer an embryo, as embryo is all in egg. But development still continues outside of the egg
Comparative embryology
2-day chick
- Marcello Malpighi, 1672, dorsal, looking down
- Lillie, 1908, ventral looking up with a dissecting scope
- 3d image, superimposing 2 images
What are the two main patterns of cleavage?
- Holoblastic (complete) cleavage
- Meroblastic (incomplete) cleavage
Tell me about the types holoblastic (complete) cleavage?
Tell me about the types of meroblastic (incomplete) cleavage
What are the types of cell movement during gastrulation?
What are these?
Why is rearranging cells crucial?
- Rearranging cells is crucial to make the right structures, cells give rise to tissues, give rise to organs
- Early patterns of development are crucial for getting cells, not only into the correct germ layer, but into the right place to set up the body axes
Naming the parts and layers
- Once in the right place, other signals kick in, forming the right cell types/tissues/organs in the right place.
- The evolution of pharyngeal arch structures in the vertebrate head
The cells that form the gills supports in fish form the middle ear bones of mammals, and jaw structures in amphibians, birds and ‘reptiles.
German embryologists
- The pattern known as von Baerian divergence, as illustrated by the embryos of four vertebrates, fish, hen, cow and human, shown at three different stages – early, middle and late. Note the pattern of early similarity giving way to later differences. (Redrawn from A Theory of the Evolution of Development, John Wiley & Sons, Ltd., 1988.)
Keeping track of moving cells
A huge part of understanding development is understanding what cells are doing. The exciting stuff is happening inside the body of the embryo, so how do we follow that?
Direct observation of living embryos
Conklin’s work published in 1905 is amazing. I was still using it to help understand tunicate development in 2000-2004!
Dye marking
Evolutionary embryology
Summary
- What development and embryology is.
- The origins of developmental biology.
- The frog’s life cycle.
- Patterns of cleavage, early development, and homology.
- The importance of embryology/dev biology across the discipline.
How does a fertilised egg (zygote) become an animal?
Embryonic development is a timed controlled process whereby a single celled, unspecialized zygote divides and selectively activates expression of genes to produce a complex organism composed of many cell types.
1. Proliferation and growth
2. Differentiation
3. Morphogenesis
Most cells in a multicellular organism have the same genome or DNA. Genes must be turned on and turned off differentially during development.