Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content +++ 1. OVERVIEW ++ Similar to DNA structure and synthesis, these subjects are closely related to Hematology/Oncology and Microbiology sections Thus, much of the focus is, as usual, on pharm and key disease applications (e.g., sickle cell anemia) In addition, 2 Biochemistry-specific topics that tend to show up on Step 1: Collagen synthesis and the lac operon +++ 2. REGULATION OF GENE EXPRESSION ++ There are several ways gene expression is regulated Initiation requires transcription factor binding to promoters (directly upstream of the gene) Promoters are often cell-type specific TATA and CAAT boxes are common features of promoters Expression is regulated by enhancers and silencers (anywhere around the gene) Methylation of DNA (CpG islands) mutes expression (see Chapter 2) Histone modification also regulates expression Methylation of histones usually mutes expression Acetylation of histones activates expression The lac operon is the example Step 1 likes to use to integrate these concepts Set of co-expressed genes used by bacteria to activate lactose metabolism when lactose is available and glucose is not Two regulatory steps must occur together to express the lac operon Low glucose—activates CAP (binds enhancer) High lactose—removes repressor protein (binds repressor) Mutations that disrupt gene regulation can be just as damaging as mutations in the gene's protein-coding region Protein deficiencies In beta-thalassemia, mutations can occur in the promoter → less production of functional protein Clinical: Anemia, hemolysis, weakness/fatigue Increased activity Myc is a transcription factor that controls cell proliferation Burkitt lymphoma, an aggressive form of cancer more common in children → caused by chromosomal translocation causing constitutive Myc expression Clinical: Rapidly growing tumors on the jaw/face (endemic variant) or abdomen (sporadic); tumor lysis, hyperuricemia ++ Figure 3-1. Regulation of gene expression. Graphic Jump LocationView Full Size||Download Slide (.ppt) ++ Figure 3-2. The lac operon. Graphic Jump LocationView Full Size||Download Slide (.ppt) ++ Figure 3-3. Glucose and the lac operon. Graphic Jump LocationView Full Size||Download Slide (.ppt) ++ Figure 3-4. Lactose and the lac operon. Graphic Jump LocationView Full Size||Download Slide (.ppt) +++ 3. TRANSCRIPTION ++ Four major types of RNA are found in the cell Ribosomal RNA (rRNA) is part of the ribosome, the main actor in translation Synthesized by RNA polymerase I Messenger RNA (mRNA) encodes protein sequences Synthesized by RNA polymerase II Processed from heteronuclear RNA initially synthesized from DNA sequence in the nucleus Amatoxins (poisonous mushrooms) inhibit RNA Pol II → apoptosis Transfer RNA (tRNA) links each mRNA codon into its corresponding amino acid Synthesized by RNA polymerase III Micro RNA (miRNA) are short RNA sequences that do not encode protein Regulates expression of proteins Binds mRNA and prevents translation and/or tags for degradation RNA is processed to become mRNA Poly-adenylation tails and 7-methylguanosine triphosphate caps are added to stabilize each end of ... Your Access profile is currently affiliated with '[InstitutionA]' and is in the process of switching affiliations to '[InstitutionB]'. Please click ‘Continue’ to continue the affiliation switch, otherwise click ‘Cancel’ to cancel signing in. Get Free Access Through Your Institution Learn how to see if your library subscribes to McGraw Hill Medical products. Subscribe: Institutional or Individual Sign In Username Error: Please enter User Name Password Error: Please enter Password Forgot Password? Forgot Username? Sign in via OpenAthens Sign in via Shibboleth You already have access! Please proceed to your institution's subscription. Create a free a profile for additional features.