Concepts and terminology Flashcards
What are changes in cell fate accompanied by?
-Changes in cell fate are accompanied by molecular changes
What are the 2 options that restriction in cell fate is controlled by?
- Option 1 Mosaic development(cell autonomous specification)
- Option 2 regulative development(conditional specification)
What is Option 1 Mosaic development(cell autonomous specification) ?
Information is inherited from parental cell
What is Option 2 regulative development(conditional specification)?
Cell influenced by its surrounding, or position, within the embryo
What is Weismann’s nuclear determinants.?
- We have a once cell embryo and with 4 different factors
- After the first cell division/cleavage, the factors are inherited differently by the 2 daughter cells
- After the second division, each of the 4 cells, each of the cells inherit a different factor.
What is Roux’s experiment on determination?
- We take a fetilised frog egg and divided into daughter cells
- First clevage happens down the midline of the embryo
- Roux put a hot needle in the left blastomere and that caused that cell to die.
- This resutled in a normal half embryo on the right hand side and dead tissue on the left
What does Driesch’s separation of sea urchin blastomeres demonstrate?
Driesch’s separation of sea urchin blastomere’s demonstrates regulative development
What do the Aba and Abp cells in early C elegans larva give rise to?
-Early C elegans embryos that pharyngeal tissue will be derived from the Aba cell and its sister cell Abp will give rise to muscle in trunk or tail region of the embryo
What happens if you flip the position of Aba and Abp cells?
If you flip the position of Aba and Abp cells, you find blue tissue will give rise to tissue in the head and the red cell will give rise to tail region
What does fate mean?
What will normally happen to a cell during development
What does commitment comprise of?
- Specification
- Determination
What is specification?
What tissues will develop in an autonomous environment
What is determination?
-An irreversible change in potential
What is differentiation?
A restriction of potential with molecular/biochemical changes
What do totipotent cells give rise to?
Totipotent can give rise to all tissues
What do pluripotent cells give rise to?
Pluripotent can give rise to many but not all tissues
What does restriction in potential depend on?
Restriction in potential often depends on inductive interactions from neighbouring cells
What is competence?
Ability to respond to an inductive signal
What does spemann and mangolds classic 1924 experiment define?
-Spemann and mangold’s classic 1924 experiment defined an inducing tissue with organiser activity
What does permissive induction create?
-Permissive induction would create the environment where other factors can act to cause a tissue to be induced
What are the 2 broad types of instructive induction?
- Appositional
- Morphogen gradient
What is appositional instructive induction?
-This is where the instruction is passed by the close apposition or bringing together of 2 different tissue types
What is morphogen gradient instructive induction?
- Localised signal of morphogen
- That morphogen is diffusible and diffuses from its localised source
- As a result of that diffusion there are different concentrations of the morphogen across the embryo
What is a morphogen?
-A Morphogen is a diffusible molecule that triggers different cell fates at different concentrations
What happens to morphogen gradients within the embryo?
-Gradients need to be formed within the embryo and cell fate and changed accordingly
What can morphogens provide?
-Can provide positional information within the embryo
What genes confer positional identity and what do the drosophila antennapedia have instead?
Homeotic(eg Hox) genes confer positional identity:
-Drosophila Antennapedia mutants have legs instead of antennae
What do homeotic genes regulate?
-Regulate the development of anatomical structures(identified in insects to control segment identity)
LOOK AT EXAMPLE OF HOMEOTIC GENES IN NOTES
NOTES
What does Turing’s reaction-diffusion model propose?
-This proposes a diffusible activator that activates a diffusible
inhibitor of itself
What are Turing patterns?
- If the activator diffuses, it induces an inhibitor that also is diffusible. The inhibitor inhibits the activator
- As there’s no activator now there’s no need for the inhibitor and it disappears.
What are the steps to form a protein?
- Regulatory region assembles RNA polymerase to generate RNA
- RNA is transcribed and produce hnRNA containing both introns and exons
- RNA is spliced leaving exons and matured with a 3’ A tails and 5’ cap
- RNA is translated then into a protein
What are changes in cell fate reflected by?
Changes in cell fate are reflected by changes in gene expression
What secretions allow cells to communicate?
Secreted factors and other signals allow cells to communicate
What other levels does additional control occur at other than gene expression?
Additional control at level of translation, post-translation, epigenetic changes.
