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Chapters 18 & 19
Bacteria
Viruses & Operon Systems
Key Topics for Ch. 18 & 19
Chapter 18
Topic
Viruses: DNA, RNA (retroviruses)
Lytic & Lysogenic Cycle
Pgs.
334-342
337-339
Bacteria:
346-350
Genetic recombination
Plasmids & Conjugation
Transformation (Lab)
Transposable elements
Lac Operon System
351-352
353-356
Regulating Gene Expression
Chapter 19
DNA & Chromatin packing into chromosomes
Oncogenes & Tumor-supressor genes (Cancer)
Transposons (B. McClintock) w/Indian corn
Pgs.
360-361
370-373
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
DNA
Herpesvirus
Poxvirus
Papovirus (warts)
RNA
Ebola
Infuenza
HIV
Measels, Mumps
Rabies
West Nile
HIV Infection (pgs 340-342)
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
http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter20/animations.html
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. 351-352)
• 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.
http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter20/animations.html
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
http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter18/animations.html#
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
http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter18/animations.html
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
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•
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•
Review of DNA & Genome
Oncogenes & Proto-Oncogenes
Tumor Supressor Genes
McClintok’s transposons
359-362
370-373
375-376
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. 370-371
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. 16-20)
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•
Cover sheet: (Name, Period, Unit #3 Ch. 16-20)
Pre-Lab: Bacteria Transformation (pGlo lab) – pick up
Pre-Lab: Analysis of Lambda DNA w/Gel Electrophoresis
Videos:
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–
–
–
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. 16-20)
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•
•
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# Questions
Chapter 16: History/Discovery of DNA replication
Chapter 17: Protein Synthesis (gene expression)
Chapter 20: Recombinant DNA Technology
Chapter 18: Gene regulation & Viruses
Chapter 19: Cancer Review/Transposons
15
18
14
8
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.