Gene Control Summary

Gene regulation allows cells with the same genetic information to develop into different types of cells.
Operon: A cluster of related genes and DNA control sequences that control them (e.g., lac operon).
Promoter: Site where RNA polymerase attaches and initiates transcription.
Operator: DNA segment between the promoter and genes; acts as a switch by binding a repressor protein.

Eukaryotic gene expression regulation is more complex than in bacteria due to a longer pathway from gene to protein.
DNA Packing: Cells may use DNA packing for long-term inactivation of genes, such as X chromosome inactivation in female mammals.
Transcription Factors: Proteins that bind to DNA sequences called enhancers and the promoter to regulate transcription initiation.
RNA Processing: Includes the addition of a cap and a tail, removal of introns, and RNA splicing.
Alternative RNA Splicing: Generates different mRNA molecules from the same starting RNA molecule, producing multiple polypeptides from a single gene.
microRNAs (miRNAs): Small RNA molecules that can bind to complementary sequences on mRNA, regulating gene expression.
RNA interference (RNAi): Blocking of gene expression by siRNAs.
Cell Signaling: A signal molecule binds to a receptor protein, initiating a signal transduction pathway that leads to a specific response inside the target cell.
Homeotic Genes: Master control genes that regulate groups of other genes to determine body parts in specific locations during early embryonic development.

Plant cloning is used to reproduce plants with specific traits.
Nuclear Transplantation: Replacing the nucleus of an egg cell with a nucleus from an adult body cell.
Reproductive Cloning: Results in the birth of a new animal via nuclear transplantation.
Therapeutic Cloning: Produces embryonic stem cells for therapeutic purposes, not a living organism.
Embryonic Stem Cells (ES Cells): Can divide indefinitely and develop into specialized cells.
Adult Stem Cells: Can generate replacements for some of the body’s cells but are more limited than ES cells.

Cancer involves changes in gene expression that allow cells to escape normal growth controls.
Oncogene: A gene that causes cancer.
Proto-oncogene: A normal gene with the potential to become an oncogene.
Tumor-Suppressor Genes: Inhibit cell division; mutations can contribute to cancer development.
The development of a malignant tumor involves a gradual accumulation of mutations.
BRCA1 and BRCA2: Genes associated with inherited breast cancers.
Most cancers arise from mutations caused by carcinogens.

Avoidable behaviors like tobacco use, alcohol consumption, and excessive sun exposure affect cancer risk.
Dietary choices like plant fiber, less animal fat, and certain vitamins can reduce cancer risk.

Tumor evolution occurs through overproduction, variation, and differential survival of cancer cells with advantageous mutations.