L1 - Introduction to Developmental Biology Flashcards
What are the implications of development not stopping at birth?
The UK population is ageing faster than its growth
How much of the UK welfare budget is spent on pensioners?
55%
What are the 3 experimental approaches to developmental biology?
Animal models
Microscopy
Genetics
What is the epigenesis theory?
Organisms develop progressively through the generation of new structure and forms
Who came up with the epigenesis theory?
Aristotle
345 BC
What is the preformationism theory?
Organisms develop from miniature versions of themselves - homunculus
Who came up with the preformationism theory?
Nicolaas Hartospeker
1695
What is cell theory?
All organisms are composed of one or more cells
The cell is the most basic unit of structure, function, and organization
All cells arise from pre-existing, living cells
What led to discovery of the cell?
Microscope technology
Robert Cooke
1665
How cells become different from each other - germ plasm determinants theory
Cells may show a subset of the programme available – somatic cells
Cells may show the whole programme – germ cells
Who came up with the germ plasm determinants theory?
Friedrich Leopold August Weismann
1880
Experimental demonstration of Weismanns theory method
- Took fertilised frog egg and allowed it to develop to 2 cell stage
- Burned half
- Only half developed with cell fate – disrupted cell-cell signalling
Wilhem Roux
1888
How cells become different from each other - induction theory
- Took sea urchin egg and allowed it to develop to 2/4 cell stage
- Separated the cells from each other and allowed them to develop
- Each of the cells lead to the development of a full embryo
Who came up with the induction theory?
Hans Driesch
What are the two ways cells communicate with each other via cues?
Intrinsic cues – cell differentiates into another
Extrinsic cues – cell influences/instructs another cell
What are some examples of changes in cell behaviour?
Cell division – asymmetric or symmetric
Cell adhesion – condensation or dispersal
Cell shape – epithelial or epithelial to mesenchymal
Cell migration
Cell death
What are the four types of cell-cell communication?
Paracrine
Autocrine
Juxtacrine
Endocrine
What is paracrine communication?
Shh, Wnt, TGFb, BMP, FGF signalling
Cell secretes ligand that binds to receptor on a neighbouring cell
What is autocrine communication?
Shh, Wnt, TGFb, BMP, FGF signalling
Cell secretes ligand that binds to receptor on the same cell
What is juxtacrine communication?
Notch signalling
Short distance direct communication
Signal reception requires cells to be competent and have…?
Permissive environment, receptor and transduction components
What are the two types of signals?
Instructive
Permissive
What are instructive signals?
Initiates a new program in the cell
What are permissive signals?
Provides a favorable environment for a specific program
Signals can act as morphogens
Instruct distinct cell fates according to their concentration
What is involved in signal transduction cascade?
Used to transmit information to the nucleus
Cell surface, cytoplasmic and nuclear proteins that relay signals from cell surface to nucleus
Signal transduction pathway method
Reception – ligand binds to a cell surface receptor and activates it
Transduction – receptor activation induces the transduction of the signal from membrane to nucleus via a cascade of secondary messenger activation
Response – transcription factor is activated and induces transcription of target genes
If gene content is identical in all cells what dictates the different proteins?
Transcription/translation dictate protein content
At what different levels do cells operate to control the gene program?
Production of mRNA
Processing/stability of mRNA
Production of proteins
Activity of proteins
What are the two ways the genetic programme is controlled at the level of gene transcription?
Differential gene expression
Enhancer mediated control of gene expression – binding of transcription factors
What is tissue homeostasis required for?
Essential for normal development, growth and repair
How is tissue homeostasis achieved?
Through the control of cell division and cell death via
- Negative feedback loop
- Stem cell mediated repair
What does disruption of tissue homeostasis cause?
Causes diseases and contributes to ageing and degeneration
Excess of stem cell self-renewal leads to?
Tissue hyperplasia
Tumorigenesis
Depletion of stem cells leads to?
Tissue degeneration
Tissue ageing
What is produced from ectoderm?
Epidermis
Neurons
Pigment cells
What is produced from mesoderm?
Muscle cells
Red blood cells
Tubule cells
What is produced from endoderm?
Lung cell
Pancreatic cell
