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From Gene To You
A Look at Chapters 14-21
DNA as Genetic Material
Deoxyribonucleic Acid
Hershey & Chase
Hypothesized the structure
Structure of DNA
Nitrogen Base
 Amounts
vary from species to
species
 Nitrogen Rings
 Purines are double ring bases
Adenine,
Guanine
Structure of DNA con’t
 Pyrimidines
Thymine,
are single ring bases
Cytosine
 A-T
uses two hydrogen bonds
 G-C uses three hydrogen bonds
5 Carbon Sugar
 Called
Deoxyribose
Structure of DNA con’t
Phosphate Groups
 Bond
with Sugar to form
backbone
The Double Helix
Watson & Crick used x-ray testing,
previous studies to come up with
double helix model
Sugar-Phosphate backbone with
Nitrogen Base rungs
10 Layers (rungs) per turn
The Double Helix con’t
Base Pairing allows for equal
amounts on each strand
Anti-parallel: one strand is oriented
3’ to 5’, the other 5’ to 3’
Dictates complements, buts allows
for infinite variation
DNA Organization
Packaged with proteins to form
matrix called chromatin
Coiled around Histones to form
Nucleosomes.
In non-dividing cell:
 Euchromatin Heterochromatin
The Structure of RNA
Ribonucleic Acid
Sugar is Ribose, not deoxy
Uracil replaces Thymine as the
compliment of Adenine
Single stranded
Protein Synthesis
A little lesson in logic………
 Traits
are the end products of
metabolic processes regulated by
enzymes or created by
polypeptides
 DNA codes for all enzymes
 DNA codes for all polypeptides
Protein Synthesis con’t
 Therefore…..the
DNA needs to
be read and somehow changed to
be useful to the cell and
organism
Process is called Protein
Synthesis
Protein Synthesis con’t
Three steps:
Transcription
 Synthesis
of RNA using DNA as a
Template
RNA processing
 Modifies
the RNA to make it
functional
Protein Synthesis con’t
Translation
 Proteins
are synthesized
according to genetic message of
sequential codons along mRNA
Three types of RNA complete
the process
Protein synthesis
Types of RNA
mRNA (messenger) is the
template for Amino Acids to
form the polypeptide
 Codon:
triplete group of
nucleotides that codes for specific
AA’s
 64 codons = 20 AA’s
Types of RNA
tRNA (transfer) transports AA’s
to proper place on the mRNA
template
 Anticodon
is the compliment of the
mRNA codon (mirror)
rRNA (ribosomal) builds the
ribosomes
Protein Synthesis- Transcription
Nucleotide sequence transcribed
from DNA to compliment mRNA
mRNA carries code to Ribosome
Initiation:
 RNA
Polymerase unzips DNA
Transcription con’t
Elongation:
 RNA
Polymerase unzips and
assembles mRNA using DNA
template
Termination:
 RNA
Polymerase reaches
AAAAAAA, (stop Nucleotides)
transcription
Protein Synthesis- RNA
Processing
Code is proofread and modified
before leaving Nucleus
Makes a functional mRNA
Eliminate Introns so specific
proteins can be made by Exons
Introns may be key to cell
variation
Rna Processing
Protein Synthesis- Translation
tRNA is interpreter between the
base sequence mRNA and the
AA sequence in Polypeptide
Proteins coordinate the pairing of
tRNA anticodons to mRNA
codons
Translation con’t
Initiation
 Takes
the mRNA and attaches to
initiator tRNA and 2 ribosomal
subunits to assemble ribosome
Elongation
 Add
AA’s 1 by 1 to Initial AA’s
Translation con’t
 Codon
recognition used to assembe
the peptide bonds (hydrogen bonds)
to form the polypeptide
Termation
 UAA,
UAG, UGA are stop codons
 Completed Polypeptide, last tRNA,
and Ribosomal subunits released
translation
The Genetics of Viruses
Cell Specific
A Nuclei Acid surrounded by a
Protein Coat (Capsid)
A membrane coats some viral
Capsids called an Envelop
Can kill cells, produce toxins
Viruses con’t
Some partially damage cells that
eventually regenerate (Flu)
Some permanently damage cells
that do not reproduce (Polio)
Viral Life Cycle-General
Infect host cell with viral Genome
Co-Opt Host’s Resources to:
 Replicate
Viral Genome
 Manufacture Capsid Proteins
Assembling of new viral Nucleic
Acid for next generation
Viral Life Cycle
Somewhat specific Life Cycles
Lytic Viral Life Cycle is where
replication results in death or lysis
of host cell
Are considered Virulent
Lytic Cycle:
Lytic Cycle
Penetration-using enzymes to
destroy host cell DNA, and to
replicate viral DNA
Transcribes viral DNA into RNA
Translates RNA to proteins
Assemble proteins and DNA into
new Virus
Lytic Cycle con’t
New viral proteins erupt from
host cell, destroying the host
cell
Off to new cell to begin anew
Lytic Cycle
Lysogenic Cycle
Viruses co-exist with host by
incorporating viral genome into
host genome
Called Temperate Viruses because
either Lytic or Lysogenic
Lysogenic Cycle con’t
Penetration- like Lytic cycle, but
does not destroy host DNA
Inserts by Genetic Recombination
(Crossing Over) into host genome,
called a Provirus (Prophage)
Inactive there until trigger, goes
Lytic
Lysogenic Cycle
RNA Viral Life Cycles
Sometimes- viral RNA is used
directly as mRNA
Retrovirus- a double stranded
RNA genome, use negative strand
as mRNA template
Transcribe DNA from viral mRNA
RNA Cycles con’t
Use Reverse Transcriptase to make
DNA compliment
DNA then used to either make
mRNA (Lytic) or chills
(Lysogenic)
Viral Life Cycle
Viroids
Viroids are plant pathogens
Simpler than viruses,and smaller
Small naked circular RNA
Do not encode protein, but do
replicate in host plant cells
Disrupt metabolism
Prions
Protein pathogens that cause
degenerative brain disease
Defective versions of normal
proteins
Cannot replicate, but hypothesis is
they convert normal protein to
prion protein, chain reaction
The Genetics of Bacteria
Bacteria contain 1 singular,
circular DNA with no histones
Located in Nucleoid Region of
Cell
Reproduce by binary fission
Contain Plasmids
Genetics of Bacteria con’t
Plasmids are short, circular, double
stranded DNA
Short life span facilitates
evolutionary adaptation to
environment
Genetic Recombination produces
new strains, separate from fission
Bacterial Genetic Recombination
Transformation
 Bacteria
absord DNA from
surroundings
 Special Proteins on surface
recognize and import DNA from
closely related species
Genetic Recombination con’t
Transduction
 Gene
is transferred by a virus
Bacteriophage
 During
Lytic Cycle, incorporates
Bacterial DNA, carries to new cell
when it incorporated into new
Genome
Gentic Recombination con’t
Conjugation
 Transfer
DNA between two
bacterial that are temporarily joined
 Tube is called Pilus (F-plasmids)
 R-plasmids give resistance to
antibiotics, make resistant strains
Regulation of Gene Expression
Activation of specific genes at specific
times
Most often tested example…the bacterium
E. coli (loves your digestive tract, especially
your large intestine!)
Begins with Operons, sequences of DNA
that direct biosynthetic pathways
The Operon-Four Components
Regulatory Gene produces a repressor protein
(prevents gene expression by blocking RNA
polymerase)
Promoter: a sequence of DNA which RNA
polymerase attaches to begin transcription
Operator: a sequence that blocks action of RNA
polymerase IF occupied by repressor protein
Structural Gene: DNA that codes for several
related enzymes that direct production of product
The rest of the story….
In E. coli, the lac operon (controls breakdown of
lactose) produces a repressor that binds to operator
region, so RNA polymerase can’t transcribe genes
that code for enzymes to breakdown and use
Lactose.
But….when Lactose is present, binds with
repressor, so RNA polymerase is able to transcribe
proteins
So….is called an inducible enzyme, because the
substance turns on the gene
And still more…
trp operon (enzymes for breakdown of
tryptophan), produces inactive repressor
that doesn’t bind to operator, so RNA
polymerase proceeds. When tryptophan is
available from environment, E. coli no
longer has to make it, so tryptophan reacts'
with the inactive repressor to make it active,
acts as co repressor
Called repressible enzymes
Genome Organization at the
DNA Level
Genome is plastic (changeable) in
ways that affect availability of
specific genes for expression
Some genes only work in certain
cells, at certain time, in certain
conditions (heterochromatin)
Changing Genome
Genome Organization
Repetitive-noncoding sequences
account for much of genome
 Think
these introns protect DNA
from shortening during replication
Gene amplification increases
selective DNA synthesis at certain
time in development
Genome Organization
 Some
cancer cells have multiple
copies which allows resistance to
drugs and therapy
Rearrangement of Genome
 Transposons
move DNA within
genome to increase or decrease
protein production
Genome Organization
Immunoglobulins
 During
cellular differentiation,
rearrange the DNA that encodes
antibodies, allows to recognize
non self, become b-lymphocytes
(white blood cells)
Mutation
Mistakes in genetic transmission
1 in 1x106 genes in meiosis and
mitosis
Alteration in number and structure
of chromosomes
Alteration in specific allele
Chromosomal Mutation
Nondisjuction: where sister
chromatids fail to separate
 Anueploidy-abnormal
number of a
certain chromosome
Trisomic,
Monosomic
 Polyploidy-two
sets
or more complete
Chromosomal Mutation con’t
 Triploidy,
Tetraploidy
Structure:
 Deletion,
Duplication,
Translocation, Inversion
Gene Mutations
Mutations that effect a single gene
or nucleotide
 Framshift,
Gene Point
Cancer…not funny
Results from genetic changes that
effect the cell cycle
Lack controls of growth and
division in somatic cells
Caused by a mutation of a normal
gene or by a viral agent
More Cancer….
Random and Spontaneous
Some Environmental causes
 Virusus
 Carcinogons
Oncogene- cancer causing gene
And still more Cancer….
Whatever the cause, the
mechanism is still the same
A mutation of the Genes that
control growth and tumor
suppression
Normally, more than one oncogene
is mutated to cause cancer
Viruses and Cancer
Transform cells by inserting viral
nucleic acids into host DNA
Is a permanent addition
15% of human cancers worldwide
Examples:
Viral Cancers
Retrovirus-Leukemia
Hespervirus-Mononuclous
Papvavorius-Cervical Cancer
Hepatitus B- Liver Cancer
DNA Technology
Practical goal is the improvement
of human health and food
production
Allows gene to be moved between
species
Prodution of antibiotics,
antibodies, fermentated products
Cloning
Recombinant DNA Technology
Technique used for recombining
genes from different sources In
Vitro and transferring this
recombinant DNA into a cell to be
expressed
Started in ’75 with Bacteria
Recombinant DNA con’t
Allows genes to move across
species barriers
Allows constuction of recombinant
DNA
Methods for purifying DNA and
proteins
Recombinant DNA con’t
Vectors for carrying recom DNA
into cells and replicating it
Techniques for determining
nucleotide sequences of DNA
Restriction Enzymes
Major tools of recombination
Cut DNA into short segments at
specific points
The the sticky ends (single
stranded overlaps)of the DNA
form bonds with the compliment
Restriction Enzymes
The recombinant DNA is carried
by Vectors
 Vectors
are generally either bacterial
plasmids, or viruses
Then the DNA is incorporated
Polymerase Chain Reaction
Called PCR
This quickly amplifies DNA In
Vitro
Used in crime scenes, prenatel
diagnosis from single cell, also
with the wolly mammoth, the idea
behind Jurassic Park
The Genome Project
Done by a variety of methods…..
Linkage mapping using markers
Physical mapping by cutting DNA
into identifiable fragments, then
overlaps
Sequencing DNA-by PCR,
Chromosome Walking
Chromosome walking
Human\\Library\sys\HOME\tmahan\Download video\Genome
Timeline.exe Genome Timeline
The Human Genome Project
The Human
Genome Project
Why Analyze The Genome?
Confirms Evolutionary Connection
to Distant Organisms
To Study gene expression to
determine which genes are active at
certain species of development
Why Analyze The Genome?
To determine gene function to
show mutation effects on protein
production
 Helps
to understand metabolic
abnormalities
Applications of Genome Data
Genetic Counseling for
prospective parents
 Show
possible traits by figuring
probability after studying
possible recombinants
 Carrier Recognition- of Parents
Application con’t- Counseling
Fetal Testing
 Amniocentisis-
14-16 wk,
looking for specific chemicals in
amnionic fluid
 PCR amplification for gene
presence
Application con’t- Counseling
Fetal Testing con’t
 Chronic
Villus Sampling (CVS)down by karyotyping at 8 to
10wks
Applications- Gene Therapy
Replace or Supplement defective
genes with functional
Normal genes introduced into
Somatic cells
 But…..can
we control protein
production?
 Does new harm other cells?
Applications- Gene Therapy
Pharmaceutical applications
 Human
Insulin
 Growth Hormone
 Tissue plasminogen activator (TPA)
 Engineer protein blocks to mimic or
block surface receptors (HIV)
Applications- Gene Therapy
Pharmaceutical applications con’t
 Vaccines-
Harmless variant or
derivative of a pathogen that stimulates
the immune system to fight the
pathogen
 Two types- Inactive, Active
 Recombinant DNA techniques used to
produce
Applications- Forensics
DNA Fingerprinting- marker testing
PCR to amplify small samples
But…….what do we do with the
DNA data gathered??????
How reliable?
Things that make you go….hmmmm
Should Genome Factor for jobs?
Who gets to examine your genes?
Costs? Insurance gets the bill?
Are vectors safe?
Who approves new products?
Who do we test them on?