Watson Crick Franklin Wilkins Franklin s photo below proved model on left to be correct for DNA 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 1953 MOLECULAR 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
Proof of double helix
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 06 Lise Meitner Nobel Prize Otto Hahn Nobel Prizes First to discover structure of DNA First to describe the physics to split the atom
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
Nucleic acid (polymer) = chain of nucleotides (monomers) B B B B B P S P S P S P S P S phosphate P B S Base = A, G, C, T sugar Nucleotide (DNA or RNA)
Sugar phosphate base Nucleic acid Double helix of nucleic acid Nucleotide
Base Pairing in DNA double helix G-C A-T C-G T-A
Only one base pairing is possible
Nucleosome = protein + DNA Protein DNA Nucleosome (a)
Nucleosomes
Heterochromatin = inactive DNA = condensed Nucleosome DNA Euchromatin = active DNA = decondensed Fig. 13.11
DNA Replication
DNA replication: One double helix forms two identical double helices
Double Helix separates New strands forms by base pairing
T A C A T G Double helix separates A T C A G T
New nucleotides are added to the old or original DNA nucleotides by base pairing with the help of enzymes (not shown here) Base pairing
Mutant normal Fig. 11.08
Protein Synthesis
Review Protein gives life structure Protein gives life function Amino acid sequence gives protein its structure and function Question: How is amino acid sequence determined?
Yeast Fruit Fly Worm Green Plant 6034 genes 13,061 genes 19,099 genes 25,000 genes Gene = section of DNA that codes for amino acid sequence in a protein
DNA Transcription (m)rna (copy) Translation Protein
Retire already!!! Overview
Sugar phosphate backbone Base pairing is the genetic code G-C C-G A-T T-A
DNA double helix separates RNA nucleotides attach to DNA T replaced by U Base pairing makes RNA copy of DNA
Transcription = (m)rna copy of one side of DNA
Transcription of mrna DNA mrna transcript DNA
Codon = three RNA nucleotides = code for particular amino acid
Translation conversion of mrna nucleotide sequence (codons) into amino acid sequence of protein
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
review Codon = three RNA nucleotides = code for particular amino acid
review Translation = mrna codons place amino acids in proper order Nontranscribed strand DNA Transcription 3 5 Transcribed strand Polypeptide Codon 1 Codon 2 Codon 3 Codon 4 Codon 5 Codon 6 Translation
UV-B UV-A Sun screen products Human skin
A C G T T C C A T G C A A G G T UV light Thymine Dimer mutation DNA from U.V. light A C G T T C C A T G C A A G G T
Thymine dimer Thymine dimer removed DNA repair enzymes New DNA replaces hole left by damaged DNA
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.
Human embryos are totipotent = can become any cell in the human body Why? because it has DNA to make every cell in the body. http://www.dynamist.com/aaa/blastocyst.gif
6 day old embryo is totipotent produce all cells 4 week old embryo is pluripotent produce most cells
Salamander many tissues can be regenerated if damaged.
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 Salamander leg cells damaged Euchromatin - active Nucleosome Transcription of DNA to make new leg DNA
Polymerase Chain Reaction
Small amount of DNA left at crime scene Polymerase Chain Reaction (PCR) DNA replication After 20 replications (a few hours) over 1,000,000 helices formed
DNA DNA Restriction enzyme (Eco R1) cuts DNA into fragments
DNA fragments loaded into wells in gel (like Jell-O) Fragments (-) migrate through gel because of electric current
DNA fragments have (-) charge (+) (-)
DNA fingerprinting compares fragments of DNA formed by restriction enzymes Like a barcode
Father #1 Baby s DNA Father #2