Gene Expression and Regulation Quiz

Gene Expression and Regulation

• DNA footprinting involves amplifying DNA, adding a radioactive label, and using DNAase to randomly cut the DNA. One half retains the label; the other is not visible. This creates labeled DNA fragments of various sizes, which can be separated by gel electrophoresis based on size.

• Transcription begins with the promoter region upstream of the gene. This region contains sequences (e.g., TATA box in eukaryotes) that signal RNA polymerase where to start. TATA binding protein binds to the TATA box to create a complex and position RNA polymerase. The TATA box is typically located between positions -35 and -25 within the gene.

• Prokaryotic promoters possess -35 and -10 sequences with binding sites for sigma factors, which recruit RNA polymerase for transcription.

• Gene expression control in prokaryotes includes cis-acting elements directly affecting nearby genes and trans-acting elements (transcription factors) indirectly influencing gene expression by binding to cis-elements.

• Repression is the inactivation of gene expression. Strong promoters, with highly conserved -35 and -100 elements, bind easily to sigma factors without other DNA elements. Adding a repressor to block gene expression inactivates the promoter.

• Eukaryotic gene expression control uses TATA-binding proteins and general transcription factors near the TATA box. Enhancers (trans-acting elements) influence gene expression via increased histone acetylation (loosening DNA packaging) and reduced DNA methylation, making DNA more accessible to transcription factors.

Gene Expression - Regulation (Additional)

• Induction involves activating gene expression. Weak promoters require activators to help sigma factors bind.
• Protein degradation is another mechanism of controlling protein levels in cells. The cell uses signals (like ubiquitin) to target proteins for degredation.

Moodle Recap Quiz

• Gene expression location: Nucleus.
• RNA polymerase function: Catalyzes DNA transcription.
• Transcription factor binding site: Promoter region.
• mRNA processing step: Spliceosome, which converts primary mRNA into mature mRNA.
• Complementary DNA base pairs: Adenine pairs with Thymine.
• Amino acid carrier RNA: Transfer RNA (tRNA).
• Gene expression regulation protein family: Transcription factors.