franklin’s photo below proved model on left to be correct for dna watson crick franklin wilkins...
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Franklin’s photo below proved model on left to be correct for DNA
WatsonCrick
Franklin
Wilkins
Pauling
Most important scientific paper in
Biology in last 100 years
First time DNA double helix seen in print
By Watson and Crick,
1953
2 April 1953MOLECULAR STRUCTURE OF NUCLEIC ACIDS
A Structure for Deoxyribose Nucleic Acid
“We wish to suggest a structure for the salt of deoxyribose nucleic acid (D.N.A.). This structure has novel features which are of
considerable biological interest.”
From the original Watson and Crick article – first published “double helix” diagram
Summary of a few people involved with DNA:
Pauling and Corey – “telephone pole” model for DNA
Franklin – x-ray photos proved Pauling wrong
Wilkins – gave x-rays to Watson and Crick
Watson, Crick, Wilkins – Nobel Prizes for DNA structure
Watson & Crick Pauling and Corey
Rosalind Franklin Lise Meitner
First to discover structure of DNA
First to describe the physics to split the atom
Nobel Prize
Otto Hahn
Nobel Prizes
06
Basic Terms:DNA Nucleotide (monomer)
Subcomponents of nucleotide
sugar = deoxyribose
phosphate
bases – 4 of them
adenine (A) guanine (G)cytosine (C)thymine (T)
Nucleic Acid (polymer) – chain of nucleotides
Double helix – two chains of nucleic acids
PPPPP S S S S S
B B B B B
Nucleic acid (polymer) = chain of nucleotides (monomers)
Base = A, G, C, Tphosphate
sugar
Nucleotide (DNA or RNA)
B
SP
Fig. 13.11
Heterochromatin = inactive DNA = condensed
Euchromatin = active DNA = decondensed
Nucleosome
DNA
New nucleotides are added to the “old” or original DNA
nucleotides by base pairing with the
help of enzymes (not shown here)
Base pairing
Protein gives life structure
Protein gives life function
Amino acid sequence gives protein its structure and function
Question: How is amino acid sequence determined?
Review
Gene = section of DNA that codes for amino acid sequence in a protein
Yeast Fruit Fly Worm Green Plant
6034 genes 13,061 genes 19,099 genes 25,000 genes
DNA double helix separates
RNA nucleotides attach to DNA
Base pairing makes RNA copy of DNA
T replaced by U
Codon – group of three mRNA nucleotides
Each amino acid has at least one specific codon.
Alanine (Ala) has the codon GCU.
Glycine has the codon GGU
Tyrosine has the codon UAU
Codon 1 Codon 2 Codon 3 Codon 4 Codon 5 Codon 6
Transcribed strand
Nontranscribed strand
3’
5’
TranscriptionDNA
Polypeptide
Translation
Translation = mRNA codons place amino acids in proper order
review
A C G T T C C A
T G C A A G G T
A C G T T C C A
T G C A A G G T
Thymine Dimer mutation DNA from U.V. light
UV light
Every cell in the body has the same DNA, but each specific type of cell makes proteins unique to those cells?
In other words every cell in your body has the exact same book of blueprints but only certain pages are read in certain cells.
http://www.dynamist.com/aaa/blastocyst.gif
Human embryos are totipotent = can become any cell in the human body
Why?
because it has DNA to make every cell in the body.
6 day old embryo is totipotent –
produce all cells
4 week old embryo is
pluripotent – produce most
cells
http://www.luc.edu/depts/biology/dev/regen.gif
Salamander can re-grow new limbs because adult stem cells behave like embryonic cells.
Heterochromatin - inactive
Euchromatin - active
Nucleosome
DNA
Transcription of DNA to make new leg
Salamander leg cells damaged
Polymerase Chain Reaction (PCR)
DNA replication
After 20 replications (a few hours) – over 1,000,000 helices formed
Small amount of DNA left at crime scene
Fragments (-) migrate through gel because of electric current
DNA fragments loaded into wells in gel (like Jell-O)
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