dna and rna replication, transcription, and translation
DESCRIPTION
DNA and RNA Replication, Transcription, and Translation. Genetic Controversy Two schools of thought a. Some said protein was material b. Some said DNA was material How was the controversy settled? - The scientific experiments of Griffith, Avery, Hershey and Chase. - PowerPoint PPT PresentationTRANSCRIPT
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DNA and RNAReplication, Transcription,
and Translation
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Genetic Controversy
Two schools of thoughta. Some said protein was materialb. Some said DNA was material
How was the controversy settled? - The scientific experiments of Griffith, Avery, Hershey and Chase
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Griffith and Transformation
- 1928 - England - Trying to develop a vaccine against pneumonia causing bacteria - Two strains - S(smooth) and R(rough)
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Disease-causing bacteria (smooth
colonies)Harmless bacteria (rough colonies)
Heat-killed, disease-causing bacteria (smooth colonies)
Control(no growth)
Heat-killed, disease-causing bacteria (smooth colonies)
Harmless bacteria (rough colonies)
Dies of pneumonia Lives Lives Live, disease-causingbacteria (smooth colonies)
Dies of pneumonia
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RESULTS
- Showed that heat killed S strain
and live R strain would kill mice - Something was “transforming” the R strain to an S strain - Called it transformation - What was the material?
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Oswald Avery - 1944 - Wanted to identify Griffith’s transforming material
- Used two enzymesa. protein killingb. DNA killing
- Showed that no transforming took
place when DNA “killed”
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D. Hershey and Chase - 1952
- Working with a bacteriophage
- Virus that infects bacteria
- Made of only two thingsa. protein coatb. DNA (genetic) core
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Bacteriophage with phosphorus-32 in DNA
Bacteriophage with sulfur-35 in protein coat
Phage infectsbacterium
Phage infectsbacterium
No radioactivity inside bacterium
Radioactivity inside bacterium
Hershey and Chase
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Recap:Was DNA or protein
injected?
- DNA has phosphorus - Protein has sulfur - Used radioactive phosphorus 32P and radioactive sulfur 35S
- Let virus infect bacteria - New viruses full of 32P
DNA was being injected!
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The Components and Structure of DNA
1. Called deoxyribonucleic acid
2. Long and thread-like (twisted)
3. Many subunits linked together
4. Subunits called nucleotides
5. 1000’s in a chain-like structure
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The structure of a nucleotide
1. Phosphate group - same in all
2. Five carbon sugara. deoxyribose sugar
3. Nitrogenous base - 4
different ones that name the nucleotide
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Nitrogenous Bases
1. Are different in each nucleotide
2. Names of the four basesa. adenine (A)b. guanine (G)c. thymine (T)d. cytosine (C)
Two classes of bases
A. purines1) large
double ring
2) A & G
B. pyrimidines1) small
single ring
2) T & C
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Purine and Pyrimidine Structure
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H. Chargaff - 1949
- Studying the amounts of bases in DNA of living things
- His results showed that:a. A always = Tb. C always = G
- Called Chargaff’s rule
- Also called the base pair rule
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The molecule is completed…
- Franklin and her X-ray
diffraction picture showed
a helix - Watson and Crick addsthat it is a double helix
with bases in the middle - Called it a “spiral
staircase”
- Strands are complements of each other
- Think of a step laddera. “sides” are alternating
sugar and phosphate
groups
b. “rungs” are base pairs
1) A = T2) C = G
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Nucleotide
Sugar-phosphate backbone
Hydrogen bonds
Adenine
Thymine
Cytosine
Guanine
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Chromosomes and DNA Replication
A. DNA Can Make Copies of Itself 1. Process called replication 2. Done during S phase 3. Needed for new cells 4. DNA unwound using helicases 5. Hydrogen bonds broken between bases 6. DNA polymerase puts new nucleotides in place (A to T and C with G) 7. New copy just like original
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From Genes To ProteinsFrom Genes To Proteins
DNADNADouble-Double-strandedstranded
DeoxyriboseDeoxyriboseThymineThymine
RNARNASingle-Single-strandedstranded
RiboseRiboseUracilUracil
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RNA RNA (ribonucleic acid)(ribonucleic acid)
3 forms of RNA3 forms of RNA mRNA (messenger)mRNA (messenger) tRNA (transfer)tRNA (transfer) rRNA (ribosomal)rRNA (ribosomal)
RNA is used to take the information in DNA RNA is used to take the information in DNA and make proteins (and make proteins (gene expressiongene expression))
2 stages of gene expression2 stages of gene expression TranscriptionTranscription TranslationTranslation
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During gene expression, During gene expression, the info in DNA is first the info in DNA is first transcribedtranscribed as mRNA and as mRNA and then then translatedtranslated via tRNA via tRNA and used to build a and used to build a protein.protein.
The Big Idea…
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1. 1. TranscriptionTranscription: :
making mRNAmaking mRNAfrom DNA to from DNA to carry carry information information
to the to the ribosomes.ribosomes.
From Genes To Proteins…
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- ALL organisms - ALL organisms have a genetic have a genetic code made of code made of three nucleotide three nucleotide sequences called sequences called codons. codons.
- Codons - Codons correspond to correspond to particular AA particular AA and stop and stop signals. signals.
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The Genetic Code
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The Genetic Code
From Genes To Proteins…
2. 2. TranslationTranslation: : Using tRNA to build Using tRNA to build proteins from the proteins from the information in information in mRNA.mRNA.
- Each tRNA - Each tRNA molecule carries an molecule carries an amino acid to the amino acid to the ribosomes, by ribosomes, by matching its matching its anticodon to a anticodon to a specific codon from specific codon from the mRNAthe mRNA
http://www.youtube.com/watch?http://www.youtube.com/watch?v=NJxobgkPEAov=NJxobgkPEAo
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GENETIC MUTATIONSGENETIC MUTATIONS
MutationsMutations (gene or chromosomal) (gene or chromosomal)
Changes in DNAChanges in DNA Effect depends on where Effect depends on where mutation occurs (body or sex mutation occurs (body or sex cell) & what type of mutationcell) & what type of mutation
Can be helpful, harmful, or Can be helpful, harmful, or neutralneutral
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Different Types of Gene Different Types of Gene MutationsMutations
SubstitutionsSubstitutions = UGU to UGC = UGU to UGC Effect depends on translationEffect depends on translation
InsertionsInsertions = nucleotides added = nucleotides added
DeletionsDeletions = nucleotides deleted = nucleotides deleted
Transposons=Transposons= DNA segments move DNA segments move spontaneously from one location to spontaneously from one location to another in the same DNA moleculeanother in the same DNA molecule
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Ex. Ex.
THE CAT ATE THE RATTHE CAT ATE THE RAT
(meaningful)(meaningful)
Deletion of C =Deletion of C =
THE ATA TET HER ATTHE ATA TET HER AT
(meaningless)(meaningless)
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Types of Chromosomal Types of Chromosomal MutationsMutations
Deletions (whole or part deleted)Deletions (whole or part deleted)
Duplications (extra copies of parts)Duplications (extra copies of parts)
Inversions (reverses parts of Inversions (reverses parts of chromosomes)chromosomes)
Translocations (parts break off and Translocations (parts break off and relocate)relocate)
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Causes of Mutations?Causes of Mutations?
SpontaneousSpontaneous
Mutagens (come from Mutagens (come from environment)environment) UV lightUV light ChemicalsChemicals Carcinogens (cancer causing)Carcinogens (cancer causing)