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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 BaseAmounts vary from species to
speciesNitrogen RingsPurines are double ring bases
Adenine, Guanine
Structure of DNA con’t
Pyrimidines are single ring basesThymine, Cytosine
A-T uses two hydrogen bondsG-C uses three hydrogen bonds
5 Carbon SugarCalled Deoxyribose
Structure of DNA con’t
Phosphate GroupsBond 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 chromatinCoiled 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 enzymesDNA 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:TranscriptionSynthesis of RNA using DNA as a
Template
RNA processingModifies the RNA to make it
functional
Protein Synthesis con’t
TranslationProteins 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 polypeptideCodon: 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 templateAnticodon 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 NucleusMakes a functional mRNA Eliminate Introns so specific proteins can be made by ExonsIntrons 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
InitiationTakes the mRNA and attaches to
initiator tRNA and 2 ribosomal subunits to assemble ribosome
ElongationAdd 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
TermationUAA, UAG, UGA are stop codonsCompleted 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 GenomeManufacture 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 DNAInserts 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 diseaseDefective versions of normal proteinsCannot 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 DNAShort life span facilitates evolutionary adaptation to environmentGenetic Recombination produces new strains, separate from fission
Bacterial Genetic Recombination
TransformationBacteria absord DNA from
surroundingsSpecial Proteins on surface
recognize and import DNA from closely related species
Genetic Recombination con’t
TransductionGene is transferred by a virus
BacteriophageDuring Lytic Cycle, incorporates
Bacterial DNA, carries to new cell when it incorporated into new Genome
Gentic Recombination con’t
ConjugationTransfer DNA between two bacterial
that are temporarily joinedTube 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 genomeThink 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 GenomeTransposons move DNA within
genome to increase or decrease protein production
Genome Organization
ImmunoglobulinsDuring 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 separateAnueploidy-abnormal number of a
certain chromosomeTrisomic, Monosomic
Polyploidy-two or more complete sets
Chromosomal Mutation con’t
Triploidy, Tetraploidy
Structure:Deletion, Duplication,
Translocation, Inversion
Gene Mutations
Mutations that effect a single gene or nucleotideFramshift, 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 causesVirususCarcinogons
Oncogene- cancer causing gene
And still more Cancer….
Whatever the cause, the mechanism is still the sameA mutation of the Genes that control growth and tumor suppressionNormally, 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 VectorsVectors are generally either bacterial
plasmids, or viruses
Then the DNA is incorporated
Polymerase Chain Reaction
Called PCRThis quickly amplifies DNA In VitroUsed 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\t-mahan\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 productionHelps to understand metabolic
abnormalities
Applications of Genome Data
Genetic Counseling for prospective parentsShow possible traits by figuring
probability after studying possible recombinants
Carrier Recognition- of Parents
Application con’t- Counseling
Fetal TestingAmniocentisis- 14-16 wk,
looking for specific chemicals in amnionic fluid
PCR amplification for gene presence
Application con’t- Counseling
Fetal Testing con’tChronic 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 cellsBut…..can we control protein
production?Does new harm other cells?
Applications- Gene Therapy
Pharmaceutical applicationsHuman InsulinGrowth HormoneTissue plasminogen activator (TPA)Engineer protein blocks to mimic or
block surface receptors (HIV)
Applications- Gene Therapy
Pharmaceutical applications con’tVaccines- Harmless variant or
derivative of a pathogen that stimulates the immune system to fight the pathogen
Two types- Inactive, ActiveRecombinant 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?