Gene expression Flashcards
Why does every cell retain its embryonic potential?
Unused DNA isn’t destroyed, but it is silenced
How does the cell regulate gene expression through differential gene transcription?
Controlling access to genes by modifying histone tails to either loosen or tighten the nucleosome organization
Which modification causes nucleosomes to condense?
Methylation
Which modification causes nucleosomes to loosen?
Acetylation
How does transcription begin in eukaryotes?
General transcription factors will bind to enhancer regions and promotors and recruit RNA polymerase
How does DNA methylation stop transcription from occurring?
The condensed nucleosomes block access to promotors and enhancers, and without the transcription factors it is impossible for RNA polymerase to bind and transcribe
What are transcription factor families?
Groups of proteins with similar functional domains
How can transcription factors cause localized gene expression?
They can be tissue specific
Why are transcription factors so critical during development?
The correct combination of transcription factors need to be transcribed and translated in the right place at the right time for a gene to be expressed.
Where do the transcription factors needed to start development in a zygote come from?
The egg
Why is alternative splicing important?
It allows a cell to produce different mRNA transcripts and proteins from the same gene, so there is variation
How does the Dscam1 gene in Drosophila stop neurons from clumping and forming connections with themselves?
The gene shows alternative splicing, and allows a wide variety of the same protein to be expressed. Neurons can distinguish the different variants from the variant that they have and will only form connections with neurons with different variants
What are 3 ways to control mRNA translation to control gene expression?
- Regulate the longevity of the transcript with sequences in the 3’ UTR and polyA tail
- miRNA
- Localization
What are 3 ways to localize mRNA?
- Diffusion and local anchoring
- Localized protection
- Active transport along the cytoskeleton
How does mRNA localization occur through diffusion and local anchoring?
mRNA diffuses around the cell and is eventually held in one place by anchoring proteins in one part of the cell when a transcript floats by
How does mRNA localization occur through localized protection?
Proteins in one region of the cell protect the mRNA from degradation
What are 5 post translational modifications to regulate protein activity?
Glycosylation, phosphorylation, folding, addition of lipids/other molecules, localization
What is morphogenesis?
The development of shape and structure
What are some ways morphogenesis occurs during development?
- Direction and number of cell divisions
- shape changes
- movement
- growth
- death
- membrane composition
- secreted products
What are epithelial cells?
Cells that are tightly bound together, form layers and stacks, and won’t move as a single cell
What are mesenchymal cells?
Cells that are loosely associated and will move around
What are the 5 cell movements in embryogenesis?
Invagination, involution, epiboly, ingression, delamination
What is invagination?
Infolding of the cell sheet into the embryo to create a tube
What is involution?
The epithelial cell layer folds back in on itself and turns into the embryo to form another layer
What is ingression?
Epithelial cells become mesenchymal cells and migrate into the embryo
What is delamination?
One cell sheet splits into 2
What is epiboly?
The epithelial layer folds over itself and forms another layer on the outside of the original layer
How does a cell move?
Differential gene expression to disassemble and reassemble their cytoskeletons, change their polarity, and cell to cell adhesion
What is the basal layer of a cell layer?
The sides of the cells that are associated with other cells through membrane contact
What is the apical layer of a cell layer?
The side of a cell not associated with any other cells
What is an epithelial-mesenchymal transition?
An epithelial cell receives a signal then becomes a mesenchymal cell
What changes occur in an epithelial cell for it to become mesenchymal?
Proteins and other things anchoring the cell in place will break, cell to cell adhesion and basal lamina degrades
