Reminders…
 Test is Monday/Tuesday
 Closed note, group (my choice)
 Covers Chapters 16-20
 Review Guide will be available


Thursday.
Quiz Corrections – I’ll take re-writes.
Best you can get for the re-take is 85.
Take your time, follow the prompts.
AP Biology
Viruses
Big Questions:
What is a virus?
How does a virus function?
AP Biology
What a virus is…
 “Obligate Intracellular
Parasite”

Cannot carry out life
cycle independent of
a cell host
 Composed of:
Genome: DNA or
RNA
 Protein coat: Capsid

 Host can be: any cell
(prokaryote or eukaryote)
AP Biology
How big is a virus?
AP Biology
Prokaryotic Viruses
 PHAGES! (bacteriophages)
 2 kinds:
Virulent phages: Lytic life cycle
Temperate phages: Lysogenic life cycle
AP Biology
Eukaryotic Viruses
 More diverse than phages
DNA or RNA genomes
 Double or single stranded
 Can have lipid envelope around protein
coat

 RNA viruses (retroviruses) mutations
are very common, so permanent
immunity not possible
AP Biology
Eukaryotic Viral Replication
AP Biology
HIV Life Cycle
• RNA viruses violate
the Central Dogma!
• Code an enzyme for
Reverse
Transcriptase
• HIV destroys immune
system cells (THelper) which leaves
the body prone to
opportunistic
infections.
• Drugs try to stop viral
replication inside cell.
Ex: Protease inhibitors
Cost = $1200 month
AP Biology
Remember Protein Modifications?
 Because HIV is so compact and efficient,


it packs many of its protein strings into
one long, nonfunctional string.
In order to work, these protein strings
need to be cut into different components.
When the strings are cut up, they can
carry out their specific functions for
replication.
Protease Inhibitors prevent this
modification and limit the viral replication.
AP Biology
Plant Viruses
 Plants get viruses too!
 Look like “blotchy” pigment patterns
AP Biology
What viruses are not…
 Viruses are not the most simple kinds
of infections:
Viroids: Disease causing RNA
molecules in plants
 Prions: Disease causing protein
molecules

 Mad Cow, CJD in humans, scrapie (sheep)
AP Biology
Questions – Ask Away!
AP Biology
Questions to answer! (Chapter 19)
1. Explain how different types of viruses utilize the
2.
3.
4.
5.
6.
information system of cells to complete their life
cycles.
Compare bacteriophages and eukaryotic viruses.
Compare lytic and lysogenic cycles of viral
reproduction.
Explain the structure and function of HIV.
How do viral processes increase genetic variation
in organisms?
Compare viruses to other infectious particles.
AP Biology
Biotechnology
AP Biology
2007-2008
Biotechnology today
 Genetic Engineering
Electrophoresis
 Recombinant Technology
 Polymerase Chain Reaction
 Transgenics/GMO’s
 Cloning

AP Biology
Recombinant Technology
 rDNA is DNA with 2 or more sources
 Bacteria are used to copy DNA and
make desired proteins
Identify gene of interest and cut it out
 insert new gene into a plasmid
 insert plasmid into bacteria

 Vector – plasmid carrying new gene into host

AP Biology
bacteria can express new gene or make
copies of inserted DNA
AP Biology
Restriction Enzymes – Cut the DNA!
 a.k.a.restriction

endonucleases
evolved in bacteria to cut up
foreign DNA from viruses
 Molecular scissors that
cut between specific
bases
 “Sticky Ends” are
where the enzyme cut
allow for joining with
another piece of DNA
cut with the same
enzyme
AP Biology
Recombinant tech.
 Transformation
insert recombinant plasmid
into bacteria
 grow recombinant bacteria in agar cultures

 bacteria make lots of copies of plasmid
 “cloning” the plasmid
production of many copies of inserted gene
 production of “new” protein

 transformed phenotype
DNA  RNA  protein  trait
AP Biology
Recombinant Plasmid
 Plasmids used to insert new genes into bacteria
cut DNA
gene we
want
like what?
…insulin
…HGH
…lactase
cut plasmid DNA
Cut DNA?
DNA scissors?
ligase
recombinant
APplasmid
Biology
insert “gene we want”
into plasmid...
“glue” together
Grow bacteria…make more
gene from
other organism
recombinant
plasmid
+
vector
plasmid
grow
bacteria
harvest (purify)
protein
AP Biology
transformed
bacteria
Transgenics – organisms with foreign DNA
 Genetically modified organisms (GMO)

enabling plants to produce new proteins
 Protect crops from insects: BT corn
 corn produces a bacterial toxin that kills corn
borer (caterpillar pest of corn)
 Extend growing season: fishberries
 strawberries with an anti-freezing gene from
flounder
 Improve quality of food: golden rice
 rice producing vitamin A
improves nutritional value
AP Biology
Green with envy??
Jelly fish “GFP”
AP Biology
Transformed vertebrates
Many uses of restriction enzymes…
 Now that we can cut DNA with
restriction enzymes…
we can cut up DNA from different
people… or different organisms…
and compare it
 why?

 forensics
 medical diagnostics
 paternity
 evolutionary relationships
 and more…
AP Biology
Comparing cut up DNA
 How do we compare DNA fragments?

separate fragments by size
 How do we separate DNA fragments?

run it through a gelatin
 agarose
 made from algae

gel electrophoresis
DNA jello??
Can’t we just add those
little marshmallows?
AP Biology
Gel electrophoresis
 DNA moves in an electrical field…

DNA is negatively charged
 size of DNA fragment affects how far it travels
 small pieces travel farther
 large pieces travel slower & lag behind
DNA 
–
AP Biology

“swimming through Jello”
+
Gel Electrophoresis
DNA &
restriction enzyme
longer fragments
wells
power
source
gel
shorter fragments
AP Biology
+
completed gel
Uses: Evolutionary relationships
 Comparing DNA samples from different
organisms to measure evolutionary
relationships
turtle snake rat squirrel fruitfly
–
DNA

+
AP Biology
1
2
3
4
5
1
2
3
4
5
Uses: Medical diagnostic
 Comparing normal allele to disease allele
chromosome
with normal
allele 1
chromosome with
disease-causing
allele 2
–
DNA

Example: test for Huntington’s disease
+
AP Biology
Uses: Forensics
 Comparing DNA sample from crime
scene with suspects & victim
suspects
S1 S2 S3
crime
scene
V sample
–
DNA

AP Biology
+
Electrophoresis use in forensics
 Evidence from murder trial

Do you think the suspect is guilty?
blood sample 1 from crime scene
blood sample 2 from crime scene
blood sample 3 from crime scene
“standard”
blood sample from suspect
OJ Simpson
blood sample from victim 1
N Brown
blood sample from victim 2
R Goldman
AP Biology
“standard”
Uses: Paternity
 Who’s the father?
Mom
F1
–
DNA

AP Biology
+
F2
child
Copy DNA without plasmids? PCR!
 Polymerase Chain
Reaction
method for
making many,
many copies of a
specific segment
of DNA
 ~only need 1 cell
of DNA to start

It’s a DNA
copy machine!
AP Biology
PCR process
 What do you need to do?

in tube: DNA, DNA polymerase enzyme, primer, nucleotides
denature DNA: heat (90°C) DNA to separate strands

anneal DNA: cool to hybridize with primers & build DNA (extension)

What does 90°C
do to our
DNA polymerase?
AP Biology
play DNAi movie
Clone
 A genetically identical organism or a
group of cells derived from a single cell
AP Biology
Cloning Process
 The nucleus from a somatic




(body) cell is harvested
An egg is harvested and the
nucleus of the egg is removed
The nucleus from the somatic
cell is then transferred into the
egg
An electric shock causes the
cell to replicate
The embryo is now implanted
into the uterus to grow into a
new individual
AP Biology
Big Ideas of Biotechnology
 Genes from virtually any organism can
be cloned using plasmid transformation
or using PCR.
 Electrophoresis and restriction
enzymes are widely used in DNA
analysis.
 GMO’s and cloned animals and plants
can be given beneficial characteristics
or make needed products such as
pharmaceuticals.
AP Biology
Now you try…
http://learn.genetics.utah.edu/
Try: Science Tools/Virtual Labs
Also check out:
Epigenetics
Molecules of Inheritance
Cloning
Genetic Variation
AP Biology