32 Questions
What is the primary level of gene expression control in eukaryotic cells like photoreceptors?
Transcription
What is the function of microRNAs in gene expression?
To degrade mRNA or block translation
What is a consequence of alternative splicing of transcripts?
Production of different mRNAs and proteins from the same RNA transcript
What determines the identity and properties of a eukaryotic cell?
The types of genes the cell expresses
At which stage can gene expression be regulated after transcription?
During RNA processing, mRNA translation, and protein modification
What is the function of neurotransmitters in a photoreceptor cell?
To allow signals to be relayed to the brain
What is the primary transcript produced during eukaryotic gene transcription?
pre-mRNA molecule
What is the process of removing sections of pre-mRNA molecule called?
Splicing
What regulates alternative splicing in eukaryotic cells?
Regulatory proteins
What determines how much protein is made from an mRNA molecule?
All of the above
What are small regulatory RNAs that control mRNA lifespan and translation?
microRNAs
What is the function of microRNAs?
Both A and B
How are microRNAs formed?
Transcription of a microRNA gene
What is the result of a microRNA being perfectly complementary to an mRNA?
Cutting of the mRNA in two
What is the term for the process of selecting different portions of an mRNA to form different variants?
Alternative splicing
What is the term for the additions made to the pre-mRNA molecule to form a mature mRNA molecule?
Capping, splicing, and poly-A addition
What is the typical outcome when the miRNA is perfectly complementary to the mRNA?
The mRNA is often cut in two by an enzyme in the protein complex.
What is the role of the 'helper' proteins during translation initiation?
They ensure the correct positioning of the ribosome on the mRNA.
What is the effect of phosphorylation on the activity of eukaryotic initiation factor-2 (eIF-2)?
It turns eIF-2 'off' by inducing a shape change.
What is the purpose of regulating protein translation in a cell?
To conserve energy and resources during periods of starvation.
What is the primary function of ubiquitin in protein regulation?
To mark proteins for degradation by the proteasome
What is the result of phosphorylation on eIF-2?
Inactivation of translation
What is the outcome when the miRNA and its target have some mismatches?
The RNA-protein complex binds to the mRNA and blocks translation.
What is the common thread among phosphorylation, ubiquitination, and other post-translational modifications?
They all regulate protein activity or persistence
What is the function of miRNAs in organisms?
To reduce the expression of their target genes.
What is the result of inactivating translation initiation through phosphorylation of eIF-2?
The cell stops synthesizing proteins.
Where can proteins be found in the cell after modifications such as phosphorylation?
In the nucleus, cytoplasm, or attached to the plasma membrane
What is an example of a post-translational modification that activates a protein?
Proteolytic cleavage of the protein.
What is the net effect of phosphorylation on protein behavior?
It varies from protein to protein, with different effects
What is the fate of ubiquitin-tagged proteins in the cell?
They are taken to the proteasome for degradation
What is the role of miRNAs in the development and function of the vascular system in mice?
They promote the development of the vascular system.
What is the effect of changes in miRNA expression levels on human diseases?
They are associated with various types of cancer and cardiac hypertrophy.
Study Notes
Gene Expression Regulation
- Gene expression can be regulated at various stages, including transcription, RNA processing, translation, and protein modifications.
RNA Processing
- Pre-mRNA undergoes modifications, including splicing, capping, and poly-A tail addition, to become a mature mRNA molecule.
- Alternative splicing allows for different exon combinations from a single pre-mRNA, resulting in different mRNA molecules.
- Regulatory proteins bind to specific sites on the pre-mRNA to control alternative splicing.
Small Regulatory RNAs
- MicroRNAs (miRNAs) are small regulatory RNAs that control mRNA lifespan and translation.
- miRNAs bind to specific mRNAs, either blocking translation or causing mRNA degradation.
- miRNAs play a key role in development and disease, and changes in miRNA expression are associated with cancer and cardiac hypertrophy.
Regulation of Translation
- Translation initiation is a key step in regulating translation, involving the binding of eukaryotic initiation factor-2 (eIF-2) to the ribosome.
- Phosphorylation of eIF-2 acts as a switch, turning translation on or off.
Protein Modifications
- Proteins can be regulated after translation through removal of amino acids, addition of chemical groups, or proteolytic cleavage.
- Chemical modifications, such as phosphorylation, can activate, deactivate, or alter protein behavior.
- Ubiquitination tags proteins for degradation by the proteasome, controlling the persistence of a protein in the cell.
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