Understand how cells with similar DNA express different genes and how disrupted controls can affect growth.
Part of the free Knowledge Mountain biology library. Read an explanation, try a question, and use a memory cue to check what you can recall.
Most body cells contain essentially the same genome, but different cell types express different sets of genes. This helps a nerve cell and a muscle cell carry out different jobs.
Gene expression can be controlled at DNA packing, transcription, RNA processing and stability, translation, and protein modification or breakdown.
If a DNA region becomes tightly packed and less accessible, what is likely to happen to transcription of genes in that region?
It generally decreases.
Transcription machinery must reach the DNA. Chromatin packing can change accessibility, though actual regulation also depends on proteins and signals.
An operon includes genes controlled together using shared regulatory DNA. In the lac system, lactose-related signals and glucose availability help determine expression of lactose-use genes.
When lactose is absent, a repressor can block transcription. High expression generally requires lactose to be available and glucose to be scarce, so the cell avoids making unneeded enzymes.
A skin cell does not normally produce insulin. Does that usually mean the insulin gene has been removed from its DNA?
No. The gene is generally present but not expressed in the same way as in insulin-producing cells.
Differentiation mostly changes patterns of gene expression. This is why a cell’s identity cannot usually be explained by saying it has an entirely different set of genes.
Proto-oncogenes normally help promote cell growth or division. Changes can turn them into overactive oncogenes. Tumor-suppressor genes normally help restrain division or maintain genome integrity.
Cancer often involves multiple genetic changes. Either excess growth signals or loss of safeguards can contribute to uncontrolled proliferation.