MCB150 Terms Flashcards
In preparation for MCB250
Gene Expression
A tightly controlled process that ensures cells produce the right proteins at the right time
Environmental Signals
In bacteria, gene expression is often triggered by environmental signals, such as the presence of specific nutrients. This allows cells to efficiently use resources and compete successfully for survival
Chromatin Remodeling
In eukaryotes, DNA is wrapped around proteins to form chromatin. For transcription to begin, chromatin must be remodeled from a condensed (closed) state to a decondensed (open) state, allowing RNA polymerase to access the DNA.
Transcription
The process of creating a primary RNA transcript from DNA. This step can be regulated to control which genes are transcribed
RNA Processing
In eukaryotes, the primary RNA transcript undergoes processing to become mature mRNA. This includes splicing out introns and adding a cap and tail. Alternative splicing can result in different mRNA variants from the same gene.
mRNA Stability
The lifespan of mRNA in the cytoplasm can vary. mRNAs that remain stable for longer periods are translated more, leading to higher protein production.
Translation
The process by which ribosomes synthesize proteins from mRNA. This step can be regulated to control the amount of protein produced.
Post-Translational Modifications
After translation, proteins can undergo various chemical modifications, such as folding, glycosylation, and phosphorylation, which are necessary for their proper function and regulation.
Negative control of Transcription
Repressor Protein binds to operator sequence near lac operon promoter, preventing transcription.
Positive Control of Transcription
CAP Protein exerts positive control, CAP must bind to cAMP to attach to cAMP binding site near promoter, high glucose levels result in low cAMP, preventing CAP from binding and thus reducing transcription.
What does the positive control and negative control of transcription ensure?
These mechanisms ensure that the lac operon is only transcribed when lactose is available and glucose is scarce, optimizing the cell’s energy use.
What are the steps of gene regulation in eukaryotes?
- Chromatin Remodeling (DNA is wrapped around proteins to form chromatin)
- Transcription (pre-mRNA is synthesized, involves assembly of transcription factors and RNA polymerase)
- RNA Processing (pre-mRNA undergoes modifications: addition of a 5’ cap and a 3’ poly-A tail, and the splicing out of introns to produce mature mRNA)
- mRNA Stability (The stability and lifespan of mRNA in the cytoplasm are regulated)
- Translation (The mature mRNA is translated into a polypeptide by ribosomes in the cytoplasm)
- Post-Translational Modifications (The newly synthesized polypeptide undergoes various modifications such as folding, glycosylation, and phosphorylation to become a functional protein)
How is chromatin remodeled?
3 major ways: DNA Methylation, Histone Modification, Chromating-Remodeling Complexes
These mechanisms ensure that the chromatin structure is dynamically regulated, allowing genes to be turned on or off as needed.
How is the initiation of transcription regulated?
- Chromatin remodeling opens up DNA for transcription.
- Regulatory transcription factors bind to specific DNA sequences to recruit other proteins.
- General transcription factors and RNA polymerase II form the pre-initiation complex.
- The Mediator complex coordinates the interaction between all these components to start transcription.
What is the post-transcriptional control of gene expression?
Post-transcriptional control refers to the regulation of gene expression after transcription has occurred. Main mechanisms:
- Alternative Splicing
- RNA Interference (RNAi)
- Protein Activation/Inactivation
These mechanisms ensure that gene expression is finely tuned and responsive to the cell’s needs.
