12.1 Cell Nucleus and Gene Expression Flashcards
What does a Centromere contain? Where does it bind
•Contains a tandemly repeated 171 bp DNA sequence called α satellite DNA
•Binds to specific proteins
E.g. CENP-A protein
Where are chromosomes localized in nucleus? specific chromo examples
Related to chromosome activity
-More active chromosomes are centrally located (less peripheral)
-Less active chromosomes are more peripheral
-Chromosome 19 has a greater density of protein coding genes
•more active,
•centrally located
-Chromo 18 peripheral, less dense
What’s the interaction between distant genes?
- genes with common purpose move together
- these genes are up regulate in response to estrogen
- after estrogen there’s only 2 localized regions. coming closer together
- genes on dif regions of the same/dif chromo can come together in the nun
- may have common pool of proteins involved in the transcription process
mRNA processing machinery is localized where?
- mRNA machinery is localized to small discrete sites or speckles
- compartmentalized
What’s the nuclear matrix?
- network of proteins very resistant to solubalization. This protein network will remain if you try to break own a cell. NB in dynamics of a cell in gene transcription.
- distinct protein network
- know it exists and has protein network that’s distinct
4 Charactereistics of the Nuclear Matrix
- Insoluble in high salt and high detergent conditions
- Composed of network of crisscrossing protein fibrils
- Scaffold for protein structure
- Anchor for machinery for transcription, RNA processing
Control of Gene Expression in Eukaryotes
- Euk=highly specialized cells (liver, kidneys, etc.)
- dif between specialized cells are what’s expressed and what isn’t
- Cells become differentiated
- Still retain complete genetic information
Dolly the sheep
- Enucleated egg cells fused with cells derived from mammary gland (epithelial cells)
- Reduced serum levels caused epithelial cells to enter quiescent state (G0) (via starvation) that “unmasked” unexpressed genes
- Fused cells “activated” by brief electric pulse.
- Egg implanted in surrogate sheep
- Dolly proved that even cell has all the genetic material needed.
- enuclulatted = cell with nucleus removed
- Dolly’s Death: due to telomers. from 6 years old cell she already had shorter tellers and so that probably set her up for a faster death.
A somatic cell is a regular body cell, not an egg cell. The nucleus of the somatic cell was removed and put into an unfertilised egg cell. The process is called somatic cell nuclear transfer. The cell used as the donor for the cloning of Nam was taken from a mammary gland. The production of a healthy clone therefore proved that a cell taken from a specific part of the body could recreate a whole individual. She was cloned so she did not need any male cells to fertilize the egg and mature it. She only has one parent.
What are the 4 levels of control of Gene expresssion
- Transcription Level
- Processing Level
- Translational level
- Posttranslational
Transcription Level control
-Control over whether a specific gene is transcribed and how often.
Processing Level Control
- How a primary transcript is spliced
- how mRNA is spiced into RNA (give you 2 dif protein products)
Translational level control
- Control over whether a transcript is translated or not and if so, at what levels.
- miRNAs play a role in controlling translation
Posttranslational Control
- Mechanisms that regulate activity and stability of proteins
- some structures are degraded by proteasomes.
Gene Expression Pattern in Mouse Ex.
looking at myogenic, muogenin promoter is fused to gene that expresses a dye, a pigment. Tells that myogenic is promoting expression in the black parts in somites (early muscle development)
Gene Expression of TCA-cycle Enzymes
- TCA cycle enzyme is induced as the cells begin to metabolize ethanol and repressed when ethanol exhausted
- (repressed because cells become fermutative, turned off, down regulate their TCA enzymes)
