dna & the central dogma
TRANSCRIPT
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DNA and The Central Dogma
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Discovery - ExperimentsFrederick Griffith – Transformation Happens
Through ChemicalsInjected Mice With Strains of Pneumonia…
Live R Cells: livedLive S Cells: diedPasteurized S Cells: livedLive R with dead S cells: diedConclusion: Dead S cells can give genetic material to live R cells, making them harmful
Avery, MacLeod, McCarty – DNA is Transforming Factor
- used isolated DNA & RNA, narrowed down chemicals in bacteria
- discovered that DNA caused transformation- however, people thought transformation applied
only to bacteria
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Hershey & Chase– Confirmation that DNA is Transforming Factor
- used radioactive sulfur (proteins) and phosphorus (DNA) to track which caused transformation with viruses
- in result found only the radioactive phosphorus in the bacteria (protein capsid didn’t enter the cell)
- confirmed DNA is the transforming factor
Franklin, Wilkins, Waston, & Crick – Structure of DNA as Double Helix
- Rosalind Franklin used X-ray crystallography to photograph DNA
- Wilkins, Watson, & Crick created a model - double helix with a sugar-phosphate backbone
bonded together covalently- nucleotide bases follow Chargaff’s Rules - alternates between purines (A,G) and
pyrimidines (C,T,U)
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Meselson & Stahl – Semiconservative Replication Model
-Three different models were proposed to explain the process of DNA replication. The Conservative and Dispersive models were incorrect.- According to the semiconservative model, the original DNA strand used in replication remains intact while the new strand is completely new.
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Viruses- Consists of a capsid, plasma envelope, RNA, and
nucleic acids- Can either be a DNA virus or an RNA virus- Bacteriophages: viruses that infect bacteria
Lytic Cycle- Phage replication cycle that culminates in the death of
the host cells - Similar to a factory where the virus uses the materials
of the cell to multiply then burst from the cell (lysis)- Example: Influenza
Lysogenic Cycle- DNA becomes part of the cell and remains dormant
until triggered wherein it proceeds the same as the lytic cycle
- Each time the host cell reproduces, the genetic material of the virus reproduces with it.
- Example: The herpes simplex virus
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DNA Replication - Involves the separation of a DNA molecule into two strands that are template strands to assemble a new complementary strand - results in two identical double stranded molecules of DNA in a semi-conservative model with one new strand and one old strand
- Origin of Replication- replication bubble- Topoisomerase- Replication Fork- Helicase- single stranded binding proteins- Primase- DNA Polymerase- leading complementary strand- lagging complementary strand- Okazaki fragments- DNA Ligase
Click here for a complete explanation of DNA replication:https://www.youtube.com/watch?v=8kK2zwjRV0M
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Central DogmaDNA RNA Polypeptides/Proteins Traits- Protein synthesis
- Transcription DNA RNA- Translation RNA
Polypeptides/Proteins
- Expression Proteins traits
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Transcription- Transcription Factors- RNA Polymerase- Promoter/TATA box- Transcription initiation complex- 5’3 direction- Transcription unit- Uracil in RNA- Polyadenylation sequence (AAUAAA)/ Terminator - 5’ cap/poly A tail- RNA processing/RNA splicing
- Spliceosomes- Introns/exons- snRNP’s (small nuclear ribosomal nuclear proteins)
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TranslationStart- Triplets/Triplet code- Codons- Reading frame- 5’3 direction- tRNA (aminoacyl tRNA synthetases)- Anticodons- Wobble- Initiator tRNA/Start codon- Small and large ribosomal subunits- Translation initiation complex- E, P, A siteProcess- Elongation/Elongation factors- rRNA- Peptide Bonds- TranslocationTermination- Stop codon- Release factor- PolyribosomesEct.- Primary, secondary, tertiary, quarternary structures
Click here for a full explanation of transcription and translation:https://www.youtube.com/watch?v=itsb2SqR-R0
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Mutations- Point mutations
- Silent mutation: A mutation, usually a substitution, in which the mutated codon (or codons) still code for the same amino acid, which causes no change in the finished protein
- Missense mutation: A mutation in which a single base is changed, and changes one amino acid into another
- Nonsense mutations: A mutation in which a single base is changed, changing a codon to a stop codon
- Frameshift mutations: An alteration of the number of bases. These are the most drastic because they change he entire structure of the protein, rather than just one amino acid.- Deletion/Addition
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Operons- means “operate”- found mostly in prokaryotes- P.R.O.G. (Promoter Repressor Operator
Gene)- Lac Operons (inducible) - TRP operons (repressible)Click here for an in-depth explanation of operons:https://www.youtube.com/watch?v=10YWgqmAEsQ
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Prions - Not cells or viruses- Misfolded versions of a protein - Normally found in the brain- Infectious - Cause of several brain diseases: scrapie (sheep),
mad cow disease (cattle), Creutzfeldt-Jakob disease (humans)
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Transposons
- “jumping genes”- Discovered by Barbara McClintock, who
was studying the genetics of corn in the 40’s and 50’s
- Jump in a “cut and paste” fashion from one part of the genome to another
- Two classes of jumping genes: insertion sequences and complex trasposons