Chapter 18

Bacteria control which genes are expressed based on environmental needs. They only express genes for products needed by the cell.

A metabolic pathway's end product stops further synthesis by inhibiting enzyme activity.

A cluster of genes with related functions, regulated by a single on/off switch.

A DNA segment within the promoter, controlling gene expression in an operon.

A protein that stops gene transcription by binding to the operator.

A molecule that joins with a repressor protein to switch an operon off.

Cells control the amount of enzymes they produce by controlling the expression of the genes making these enzymes.

A gene that codes for a protein that controls the expression of other genes.

Repressors inhibit gene expression by binding to control elements or interfering with activator binding.

A specific combination of control elements and activator proteins is needed for gene expression.

Eukaryotic genes that are expressed together, even though they are located on different chromosomes, share the same combinations of control elements.

Areas within the nucleus where chromatin loops from different chromosomes congregate for gene expression, promoting coordinated transcription.

Gene expression is regulated after transcription, allowing for quick responses to environmental changes.

Acetyl groups attach to histone tails, opening up chromatin, promoting transcription initiation.

Adding methyl groups to DNA bases, this condenses chromatin reducing transcription

Tightening of DNA structure, often associated with reduced transcription.

Inheritance of traits through mechanisms not involving DNA sequence changes.

Segments of noncoding DNA that binding sites for protein, affecting gene expression.

Factors required for transcription of all protein coding genes.

Factors needed for transcription of specific genes.

Enzyme that needs general transcription factors to initiate the process of transcription.

Distal control elements that can be far away from a gene, even in introns, associated with one gene.

Proteins that bind to enhancers and boost the speed of gene transcription.

DNA regions close to a gene that control its transcription, close to the promoter.

Interact with general transcription factors and enhancers; facilitate the assembly of proteins to initiate transcription.

Complete collection of proteins required for transcription; assembles after all required factors are in place.

Multiple genetic alterations, such as activating oncogenes and inactivating tumor suppressor genes, are usually required for a cell to become cancerous. This process often takes time, explaining why cancer incidence increases with age.

Regular screening for colorectal cancer is recommended to detect and remove precancerous polyps before they develop into full-blown cancer.

Breast cancer is diverse, with several distinct subtypes identified through genomic analysis. These subtypes have different characteristics and may respond differently to treatments.

Individuals can inherit altered genes that increase their risk of developing certain cancers. For example, mutations in the BRCA1 or BRCA2 genes are associated with increased breast cancer risk.

Some viruses can contribute to cancer development by altering the regulation of genes within infected cells. This can lead to uncontrolled cell growth.

A process where different mRNA molecules are produced from the same primary transcript, depending on which segments are treated as exons or introns.

It allows a single gene to code for multiple proteins, expanding the protein diversity of a genome without needing many genes.

Alternative splicing could explain why humans have a relatively small number of genes compared to their complex protein repertoire.

Regulatory proteins can bind to specific sequences or structures on the mRNA, preventing translation. miRNAs can also bind to the mRNA and block translation.

Translation initiation factors can be simultaneously activated or deactivated in a cell, controlling the translation of all mRNAs.

The 3' untranslated region (UTR) of an mRNA molecule contains sequences determining its lifespan in the cytoplasm.

mRNA lifespan helps regulate the pattern of protein synthesis in a cell.

After translation, polypeptides undergo processing, which includes cleavage (cutting) and chemical modifications.