Key Terms
Eukaryotic regulation levels (in order)
1. Epigenetic - access to DNA
Context
The lac operon encodes enzymes to process lactose; including beta-galactosidase (encoded by the Z gene), which breaks la
Logic
If tryptophan is already available, stop making it. If it's scarce, make more.
Two conditions BOTH required for transcription
1. Glucose must be absent (so CAP-cAMP complex forms and binds the promoter) 2.
Two main mechanisms
1. Chromatin remodeling (histone modification) 2.
Imprinting
Some genes methylated in a parent's gametes remain silenced in the offspring. Environmental factors like diet can also a
Cis-acting elements
Transcription factor binding sites on the same chromosome, adjacent to the gene they regulate.
Trans-acting elements
Binding sites outside the promoter or on a different chromosome that influence transcription of a particular gene.
How they work
Transcription factors bind the enhancer; the DNA bends (aided by DNA-bending proteins) to bring the enhancer and promote
Alternative splicing
Combining different exon combinations from one pre-mRNA to produce multiple proteins
RNA-binding proteins (RBPs)
Bind to the 5' UTR or 3' UTR of the mRNA; can increase or decrease RNA stability depending on the specific RBP.
Key steps
1. eIF-2 (eukaryotic initiation factor 2) binds GTP 2.
Control point
Phosphorylation of eIF-2
Tumor suppressor genes
Normally active; prevent uncontrolled growth; when mutated, the brakes come off.
Proto-oncogenes
Normal positive regulators of the cell cycle; when mutated, they become oncogenes.