DNA and RNA Replication, Transcription, and Translation
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1 DNA and RNA Replication, Transcription, and Translation
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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 Presentation
Transcript of DNA and RNA Replication, Transcription, and Translation
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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 Bases1. 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. purines
1) large double ring
2) A & G
B. pyrimidines1) small single
ring2) 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 ladder
a. “sides” are alternating sugar and phosphate groups
b. “rungs” are base pairs1) 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 ReplicationA. 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 Proteins
• DNA• Double-stranded
• Deoxyribose• Thymine
• RNA• Single-stranded
• Ribose• Uracil
3 forms of RNA– mRNA
(messenger)– tRNA (transfer)– rRNA
(ribosomal)
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1. Transcription:
making mRNAfrom DNA to carry
information to the
ribosomes.
From Genes To Proteins…
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- ALL organisms have a genetic code made of three nucleotide sequences called codons.
- Codons correspond to particular AA and stop signals.
From Genes To Proteins…2. Translation: Using tRNA to build proteins from the information in mRNA.
- Each tRNA molecule carries an amino acid to the ribosomes, by matching its anticodon to a specific codon from the mRNA
http://www.youtube.com/watch?v=983lhh20rGY
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GENETIC MUTATIONS
Mutations (gene or chromosomal)
–Changes in DNA–Effect depends on where
mutation occurs (body or sex cell) & what type of mutation
–Can be helpful, harmful, or neutral
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Different Types of Gene Mutations
• Substitutions = UGU to UGC– Effect depends on translation
• Insertions = nucleotides added
• Deletions = nucleotides deleted
• Transposons= DNA segments move spontaneously from one location to another in the same DNA molecule
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• Ex. THE CAT ATE THE RAT (meaningful)
• Deletion of C =THE ATA TET HER AT (meaningless)
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Types of Chromosomal Mutations
Deletions (whole or part deleted)
Duplications (extra copies of parts)
Inversions (reverses parts of chromosomes)
Translocations (parts break off and relocate)
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Causes of Mutations?
• Spontaneous
• Mutagens (come from environment)– UV light– Chemicals– Carcinogens (cancer causing)
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RNA (ribonucleic acid)
3 forms of RNA– mRNA (messenger)– tRNA (transfer)– rRNA (ribosomal)
RNA is used to take the information in DNA and make proteins (gene expression)
2 stages of gene expression– Transcription– Translation
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During gene expression, the info in DNA is first transcribed as mRNA and then translated via tRNA and used to build a protein.
The Big Idea…
The Genetic Code
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The Genetic Code
