Lecture 22: Gene Regulation Flashcards
Housekeeping genes
Genes that every cell must express for basic functions(transcription, metabolism)
If all cells share the same alleles and genes why do they all look different?
Specific cells(skin cells, haemoglobin) express different genes
Examples of housekeeping genes?
-RNA polymerase
-Mitochondria ATPase
-Actin
-Succinate Dehydrogenase
True or False: All steps of the central dogma are subject to regulation?
True
What is the main way to determine cell type?
Regulation of transcription, cells won’t express unnecessary mRNAs
In both prokaryotes(operons) and eukaryotes what is regulated at transcription?
Promoter
Promoter of eukaryotic organisms?
-Made up of a TATA Box
Poly I
Poly II
Poly III
Poly I: Transcribes rRNA
Poly II: Transcribes mRNA
Poly III: Transcribes tRNA
Transcription Factors
TFII are transcription factors that must prepare the way for RNA polymerase II to transcribe DNA.
Multiple TF bind before finally recruiting the RNA polymerase II. They then give RNA polymerase permission to start transcribing
Two reasons why enhancers and silencers are special?
- They can act at a great distance up to 20000 bp away
- They can act in either orientation(inverted)
What do enhancers and silencers do?
Enhancers: Recruit activator proteins and help RNA polymerase work more efficiently
Silencers: Recruits repressor proteins and decrease RNA polymerase transcription
FAR from the promoter
Most important transcription factor ?
2D
Porkaryotic vs Eukaryotic regulation ?
Prokaryotic: Help decide whether the RNA polymerase should start transcribing
Eukaryotic: Give the RNA polymerase permission to transcribe
How do enhancers work from so far away?
- DNA folds
- The enhancers then bind to the transcription factors which are controlling the RNA polymerase
3.It will change the configuration of the transcription factors to either enhance or repress transcription
Do nucleosomes(DNA coiled around histones) prevent binding of transcription factors and transcription in general?
Yes
Heterochromatin?
Tightly wound DNA, that is not transcribed
-Dark stripes on karyotype
Eurchromatin?
DNA that is transcribed
-Light stripes on karyotype
Why can women have more than one X chromosome?
Females inactivate one of the X chromosomes by condensing it into a state that prevents transcription
What is it called when an X chromosome is turned off?
The X chromosome becomes a BARR BODY
What is the number of Barr Body?
Number of chromosomes minus one(must have one active X chromosome always)
Lyonization
Different cells will have different X chromosomes condensed. If the active X chromosomes have different alleles then different parts of a females body could have different phenotypes
Gene Amplification
-An increase in the number of copies of genes
- Cancer cells
Alternative Splicing
Sometimes while splicing out introns, exons are also spliced out this creates a protein missing a chunk. This can affect the protein function
RNA Stability
mRNAs need to constantly be degraded as new ones are constantly being created. A more stable RNA = More resistant to degradation (will stick around longer). Therefore, we want RNAs to be unstable so that RNAs can be degraded
mRNA similar to water??
The rate at which water flows out of the water reservoir is determined by the water level
Higher level = faster rate
-The rate of transcription and the rate degradation determines the level of mRNA
Translational Control
The concentration of mRNA in a cell determines how much of a protein gets made
RNA Interference
-When the cell makes small interfering RNAs that do not encode for a protein but are complementary to the mRNA of a gene
-With the help of a dicer these siRNAs bind to the complementary mRNA and block its transcription
Post-translational controls
-The regulation of proteins
-Cyclin and CDK used to regulate the cell cycle by binding together to form kinase
- Kinase helps change the function of a protein from its active form to its inactive form
Kinases
Catalyze the transfer of phosphates between substances
How are proteins destroyed?
Ubiquitin binds to proteins and then the protein with the ubiquitin binds to a proteasome, the proteasome is a complex that’s job is to destroy proteins back into amino acids that can be reused
Is regulating post-transcriptionally better?
Not necessarily.
-Rgulating before transcription is efficient since no energy is used to make mRNAs/proteins, but should a protein be required it will take a while to make the protein
-Regulating proteins post translationally is much faster but involves proteins that spend time doing nothing while waiting to be activated
