Chapters 18 & 19 Bacteria Viruses & Operon Systems

Key Topics for Ch. 18 & 19 Chapter 18 Topic Pgs. Viruses : DNA, RNA (retroviruses) Lytic & Lysogenic Cycle Bacteria: Genetic recombination Plasmids & Conjugation Transformation (Lab) Transposable elements Lac Operon System Regulating Gene Expression Chapter 19 Pgs. DNA & Chromatin packing into chromosomes Oncogenes & Tumor-supressor genes (Cancer) Transposons (B. McClintock) w/Indian corn 375

DNA & RNA Viruses See Pgs. 340

Lytic & Lysogenic Cycles of a Virus (Lysogenic:host is not destroyed)

5 Classes of Viruses-Pg. 340

Examples of Common Viruses DNARNA HerpesvirusEbola PoxvirusInfuenza Papovirus (warts)HIV Measels, Mumps Rabies West Nile

HIV Infection (pgs )

HIV infection on a White Blood Cell

Invasion of a Virus

Relative size Differences between of Viruses, Prokaryotes, and Eukaryotes

Bacterial Reproduction of DNA

Transduction

Conjugation and the transfer of the F Plasmid

Transformation Uptake of foreign DNA from the environment What we did in our lab (pGLO plasmid)

Detecting Genetic Recombination in Bacteria (pg. 347)

Insertion Sequences & Transposable Elements (pgs ) Always a part of of chromosomal or plasmid DNA Sometimes called “jumping genes”-never detach Inverted sequences are on each side of an insertion sequences. (See pg. 352) A single gene for coded for:transposase Specialized plasmids are constructed using these sequences.

Jacob & Monod Discovered Lac Operon – Nobel Prize for Discovering Control of Gene Expression

Regulation of a Metabolic Pathway

Specialized Genes Operator = "on/off" switch for operon Regulator = makes repressors to turn off an entire operon Repressor = Binds to operator, turn off gene expression Inducer = Joins with an active repressor, activates it Co-repressor = Joins with inactive repressor, converts it to active

OPERON THEORY Operon = group of structural genes regulated as a unit Several genes controlled by an operator site

Operon Complex RNA Polymerase must bind to the promoter site and continue past the operator site to transcribe mRNA

Repressible Operons (trp operon) Usually “ON” - to turn OFF: –Co-repressor needs to bind to an inactive repressor and activate it –RNA Polymerase then cannot bind and transcribe mRNA Ex. trp operon is a repressible operon: -trancription is usually on -inhibited only by tryptophan (corepressor)

Trp Operon when Tryptophan is Absent

INDUCIBLE Operons (ex. lac operon) Usually “OFF” - to turn ON: –INDUCER needs to bind to an active repressor and inactivate it –RNA Polymerase can then bind and transcribe mRNA Ex. Lac operon is an inducible operon

Lac Operon Lactose ONLY used when glucose is not present in large quantities When glucose is present, cAMP levels are low, cAMP cannot bind to CAP and initiate enzyme production

Inactive Repressor-Lactose Present

Lac Operon In absence of glucose, cAMP levels are HIGH, binding to CAP can occur Beta-Galactosidase is made

Lac Operon RNA polymerase only binds efficiently when cAMP-CAP complex is in place Lac Operon = an INDUCIBLE Operon Lactose = an INDUCER –Binds to repressor and inactivates it

Lac Operon Summary

Key Concepts for Chapter 19 Review of DNA & Genome Oncogenes & Proto-Oncogenes Tumor Supressor Genes McClintok’s transposons

Chromatin Def: complex of DNA and proteins DNA Packing Histone proteins (+ charged amino acids w/ phosphates of DNA that are - charged) Nucleosome -”beads on a string”; basic unit of DNA packing Heterochromatin -highly condensed interphase DNA (can not be transcribed) Euchromatin -less compacted interphase DNA (can be transcribed)

The Biology of Cancer (review) Oncogenes & Tumor Suppressor Genes (RAS gene)(p53 gene)

Molecular Biology of Cancer pgs I. Proto-oncogene -----convert into Oncogenes -Controls cell growth(cell cycle & levels of cyclin) -Analogy: gas pedal is stuck in the down position ***Possible Causes: -movement of DNA &/or chromosome fragments -amplification; increases the number of copies of proto-oncogene -point mutation; protein product is altered II. Tumor-suppressor genes -Considered the “Guardian Angel gene” -Example (p53 gene) -Analogy: Break pedal is stuck in the up position

Assignt. Packet #3 (Ch ) Cover sheet: (Name, Period, Unit #3 Ch ) Pre-Lab: Bacteria Transformation (pGlo lab) – pick up Pre-Lab: Analysis of Lambda DNA w/Gel Electrophoresis Videos: –True Story of the Elephant Man –DNA Blueprint of Life (3 segments) –Cracking the Code of Life –Using DNA Fingerprinting to solve crimes (2 cases shown) IQ’s x6 Cumulative Practice test (40 Quest.) – Printout results ****Be sure to Choose Chapters 16-20

Test #3 Breakdown (Ch ) Chapter 16: History/Discovery of DNA replication15 Chapter 17: Protein Synthesis (gene expression)18 Chapter 20: Recombinant DNA Technology14 Chapter 18: Gene regulation & Viruses 8 Chapter 19: Cancer Review/Transposons 2 Lab: 6 Cumulative Quest. (Ch. 1-19):12 ____________________________________________________ TOTAL Questions: 75 Topics to review: Proteins (struct. & function)-x2, Cell Respiration (glycolysis & Kreb), Diffusion/osmosis, Membrane fluidity, Genetic cross (Mendelian), Enzyme function, chromosome number after mitosis or meiosis. # Questions