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DNA and Replication. Test: Friday Nov. 19 Covers Viruses and DNA/Replication. DNA- Deoxyribonucleic Acid. DNA codes for genes which carry your genetic information. History of DNA. 1953 Watson and Crick proposed the double helix, or spiral staircase, structure of the DNA molecule
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DNA and Replication Test: Friday Nov. 19 Covers Viruses and DNA/Replication
DNA- Deoxyribonucleic Acid • DNA codes for genes which carry your genetic information.
History of DNA • 1953 • Watson and Crick proposed the double helix, or spiral staircase, structure of the DNA molecule • They were awarded the Nobel prize for this discovery
DNA Discovery • The Hershey-Chase Experiment • Bacteriophages: a virus that attacks bacterial cells. They inject genetic material and take over the cell • Radioactive markers: tag and stick to certain parts of the bacteriophage
Hershey-Chase Experiment-pg290 Bacteriophage with phosphorus-32 in DNA Phage infectsbacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infectsbacterium No radioactivity inside bacterium
Hershey-Chase Experiment-pg290 Bacteriophage with phosphorus-32 in DNA Phage infectsbacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infectsbacterium No radioactivity inside bacterium
Hershey-Chase Experiment-pg290 Bacteriophage with phosphorus-32 in DNA Phage infectsbacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infectsbacterium No radioactivity inside bacterium
Structure of DNA Chargaff’s Rules *base pairing rule of A+T & C + G Source of DNA A T G C Streptococcus 29.8% 31.6% 20.5% 18.0% Yeast 31.3% 32.9% 18.7% 17.1% Herring 27.8% 27.5% 22.2% 22.6% Human 30.9% 29.4% 19.9% 19.8%
X-Ray Evidence of DNA • Rosalind Franklin • Suggested a twisted double helix
DNA Structure • DNA structure is made up of nucleotides • Each nucleotide is made up of three parts: • Sugar (deoxyribose) • Phosphate • Nitrogenous Base • (Adenine, Thymine, Guanine, Cytosine)
Structure of DNA Nucleotide (3 parts) Hydrogen bonds (connect bases) Sugar/phosphate Backbone (sides) Key Adenine Thymine Cytosine Guanine Deoxyribose sugar is attached to all bases
Base-Pair Rule • In a DNA molecule bases pair up in predictable ways • Adenine always pairs with Thymine • Guanine always pairs with Cytosine • A = T • G = C
Base Pair Rule One side: A T A T C A T G C G GG Other side:
How the Code Works The combination of A,T,G,C determines what traits you might have, for ex. C A T C A T = purple hair T A C T A C = yellow hair
Think of the bases of DNA like letters.Letters form words....Words form sentences.... *endless combinations
All the activities of the cell are controlled by DNA. DNA is located in the nucleus of the cell. Just before cell division DNA coils to form chromosomes. A Chromosome is tightly coiled DNA. When a chromosome is unraveled, it reveals DNA’s double helix shape.
DNA Replication • When a cell divides each cell needs its own DNA • DNA must replicate and produce two identical strands of DNA in order for this to happen
Process of DNA Replication • An enzyme “unzips” the existing DNA strand • Free floating nucleotides attach themselves to each side • TWO new strands of DNA are formed for each new cell
This “double helix structure” makes it possible for DNA to make an exact copy of itself. T T T T T T T T A A A A A A A A A A A A A A A A T T T T T T T T G G G G G G G G G G C C C C C C C C C C C C C C C C C C G G G G G G G G 1 DNA “unzips itself.” 2 Free-floating nucleotides attach themselves to each side. DNAPolymerase This is known as replication.
DNA Replication Video http://www.youtube.com/watch?v=hfZ8o9D1tus
DNA Fingerprinting • The only difference between your DNA and the DNA of the person sitting next to you is the order of the DNA base pairs • Every person has a different sequence • DNA fingerprinting is a way to identify and distinguish among individual human beings