3.3 - How development is controlled? Flashcards
What is epigenetics?
Epigenetics is the study of heritable changes in gene expression without a change in the DNA sequence occurring.This change in gene expression could occur from chemical modification of DNA or histone proteins.
What is meant by totipotent?
can differentiate into any cell
What is meant by pluripotent?
can differentiate into most cells
What is a stem cell?
Unspecialized cell that can differentiated into a specialized cell
What was acetabularia experiment?
1) Swapping stalks results in intermediate/hybrid hats
2) Swapping rhizoid results in complete change of hat structure
3) Conclusion: nucleus produces chemical messengers that affect hat shape
4) The controlling structure is the nucleus
What is Gene expression ?
- When a gene is ‘switched on’ or ‘expressed’ it is transcribed into a mRNA strand which is then translated into a protein
- Proteins such as enzymes can control chemical reactions
What is Regulating gene expression ?
- All cells have the same genetic information (all cells have all genes)
- Different cells have specific games switched on and switched off
- Results in cells becoming specialized (differentiated)
How can genes be switched on and off?
- Regulation of transcription
- Epdigentics modification of DNA
What happens when lactose is absent in regulating transcription (lac operon)
1) When lactose is absent, a repressor protein binds the operator region of the gene for β-galactosidase
2) This prevents RNA polymerase transcribing the gene
3) The gene is repressed or ‘switched off’
What happens when lactose is present in regulating transcription (lac operon)
1) When lactose is present it binds to the repressor protein
2) The repressor cannot bind the β-galactosidase gene
3) RNA polymerase can transcribe the gene
4) mRNA is produced and the β-galactosidase enzyme is produced
