dna biology copyright © the mcgraw-hill companies, inc. permission required for reproduction or...
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DNA Biology
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Chargaff
DNA – The Watson and Crick model
1962 Nobel Prize“scientists were convinced that itcould not be the molecule of life”
The DoubleHelix
Rosalind FranklinX-ray crystallography
Why is DNA important?
DNA is the blueprint or recipe for how to make proteins.
Proteins are what cells are made of, their primary structure.
Proteins are what enzymes are made of, and enzymes control all the chemical reactions in living things. (metabolism)
Deoxyribonucleic acid
• Polymer composed of nucleotides.
• Nucleotides composed of:– Sugar (deoxyribose)– Phosphate– 1 of 4 different kinds of
nitrogenous bases– A T C G
What they discovered……
The Watson and Crick Model• They defined DNA
structure.– Sugar bonds to phosphate
groups alternately forming a “twisted ladder” shape.
– Ladder rungs = bases joined by hydrogen bonds
–A only bonds w/ T (in DNA) – A bonds w/ U (in RNA)– G bonds with C.
DNA and RNA Structure and Function
RNA DNA____________________Ribose Deoxyribose Nitrogenous bases – ACGU Nitrogenous bases – ACGTAlpha helix Double helixNucleus and ribosome Nucleus onlyTOOL of protein synthesis BLUEPRINT of protein synthesis
Nucleotide w/ cytosine
Transcription Translation
mRNA tRNA
Code break the Code
Triplet = codon triplet = anti-codon
Nucleus ribosome
Protein synthesis begins withDNA in the Nucleus.
Transcription (cont.)
RibosomesMade of rRNA
In the cytoplasm or on the rough ER
Site of Protein Synthesis
The Genetic Code: A triplet codeCodons: 20 amino acids, 64 possible codons
Translation: tRNA is an “Amino Acid Taxi service”
Single-stranded RNA
Anticodon complements
mRNA codon.
aa
Translation…
• The order of the tRNA molecules determines the order of the amino acids in the protein molecule.
• It’s the order and type of amino acids that give a protein it’s qualities… How? (Cow?
Ho? Howl?)
Note tR
NA leavin
g
Note bond forming…
Next tRNA arrives
anticodon
Peptide formation is primary structure of the protein!• Secondary
• Tertiary
• Quaternary• Remember?
Gene Mutation…
• changes the sequence of bases in the DNA
• are rare (one in 100 million cell divisions).
• caused by mutagens– Radiation (radioactivity, X-rays, UV light)– Chemicals (pesticides, cigarette chemicals)