Development 2: What controls development? Flashcards
What are the 3 control factors in development?
Cytoplasm (epigenetic)
External environment (epigenetic)
Genes (genetic)
During embryonic development, what normal DNA process is ‘turned off’?
Transcription
What is the cytoplasm’s role in embryonic development?
Controls metabolic cycles and instructions for driving cell division
Early development is controlled by which parent?
Maternally controlled, cytoplasm comes from mother
What is genomic activation?
change from maternal control to embryo control
Describe what happens once genomic activation has occurred.
- Embryonic DNA starts transcription = cell division
- Cell division slows down (because transcription & translation take time) = how this stage is identified
What does cell differentiation result from?
differential gene expression (certain genes are switched off = cell function)
What is differential gene expression influenced by?
the cytoplasm and the extracellular environment
Describe the results of the Experiment on frogs to test the role of cytoplasm on differentiation
Genomic equivalence = No info is lost in the early stages of development (every nucleus in every somatic cell contains all the genes for creating a whole new individual)
= Shows the cytoplasm controls the fate of a nucleus
Describe cytoplasmic segregation in development
when a factor is unequally distributed in the cytoplasm and ends up in some daughter cells but not in others, or in greater conc.s than in others
= cause differentiation of cells due to animal and vegetal poles differing in their developmental potential
Define induction in development
When a factor is secreted by some cells to induce others to differentiate
Describe primary induction in birds and amphibians
- In amphibians, cells moving over the dorsal lip of the blastopore (Spemann organiser) induce overlying ectoderm to form neural tissue
- In birds, cells moving over Hensen’s node are induced to form the CNS
The development of which sensory organ is an example of secondary induction?
the vertebrate eye
How do cells ‘know’ where they are in an animal?
By interpretating positional info = conc. gradient of a morphogen
A signal is a morphogen if …
- It directly affects target cells (does not work through an intermediary)
- Diff conc.s cause different effects