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