dna: deoxyribonucleic acid q2 wk6 d1 11/18/13. scientists of dna 1953, james watson & francis...
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Scientists of DNA Rosalind Franklin: Rosalind refined the technique of X-ray crystallography, to study DNA and produced “Photo 51” From photo 51, Rosalind determined that DNA is the shape of double helix Watson & Crick used photo 51 and published their results before Franklin Rosalind Franklin died in 1985TRANSCRIPT
DNA: Deoxyribonucleic Acid
Q2 WK6 D1 11/18/13
Scientists of DNA• 1953, James Watson & Francis Crick
were accredited for discovering the structure of DNA• Awarded the Nobel Prize for
Physiology and Medicine in 1962; Watson, Crick and Maurice WilkinsShould someone else
have received credit???
Scientists of DNARosalind Franklin:Rosalind refined the technique of X-ray
crystallography, to study DNA and produced “Photo 51”
From photo 51, Rosalind determined that DNA is the shape of double helix
Watson & Crick used photo 51 and published their results before Franklin
Rosalind Franklin died in 1985
Location of DNA• DNA is coiled in chromosomes; chromosomes
are located in the nucleus.• DNA is the shape of double helix
• Double stranded• Twisted• Similar to a spiral staircase
Draw me
Double Helix looks like…• If a DNA strand was
straightened, what would it look like???
A LADDER!
Make up of DNA• DNA is made up of Nucleotides strung together in a certain order.• Each nucleotide contains…
• Deoxyribose (Sugar)• Phosphate• Nitrogen base
• Adenine (A)• Thymine (T)• Guanine (G)• Cytosine (C)
How is DNA organized?• Sugar alternates with phosphate at the sides• The rungs (steps) of the DNA molecule are paired nitrogen bases• The nitrogen bases pair in the following way…
• Adenine ALWAYS pairs with Thymine (A-T)• Cytosine ALWAYS pairs with Guanine (C-G)
The rungs are connected at the sugars
Nitrogen bases
deoxyribose
phosphate
Nitrogen Base: PRACTICE1. Adenine -2. Cytosine -3. Thymine -4. Adenine -5. Guanine -6. Guanine -7. Cytosine -8. Thymine -
Add to notebook check
Write the appropriate pair with the listed nitrogen base…
Nitrogen Base: answers• Thymine• Guanine• Adenine• Thymine• Cytosine• Cytosine• Guanine• Adenine
1. Adenine2. Cytosine3. Thymine4. Adenine5. Guanine6. Guanine7. Cytosine8. Thymine
DNA structure: REVIEW• DNA shape = double helix• Rails = Phosphate & deoxyribose (sugar) alternate• Rungs= Nitrogen base pairs• Base Pairing Rule: Adenine – Thymine
Guanine – CytosinePurines: Adenine & Guanine; made of 2 carbon rings and nitrogen atoms.Pyrimidines: Thymine & Cytosine; made of a single ring of carbon and
nitrogen atoms
Q2 WK7 D1
DNA Replication
Purines & Pyrimidines
DNA Replication
• During the cell cycle DNA replication occurs the “S” (synthesis) phase• DNA Replication: The process of making a copy of DNA• DNA replication results in 2 identical DNA strands• DNA is copied BEFORE the cell divides
Steps of DNA Replication• Step 1: Before DNA can replicate, the double helix unwinds.
• An enzyme called “ DNA Helicase” breaks the bonds between the nitrogen bases.• Once the strands separate, proteins prevent the strands from making their
double helix shape.• Areas where the double helix separates are called “Replication forks”.
DNA unwindsDNA Helicase- Enzyme that opens the double helixReplication fork- areas where the DNA opens
Step 1
Tuesday 12/1/2015Agenda: DNA Notes: DNA Replication (Steps 2 and 3)
Activity: DNA Replication Worksheet
Homework:
DNA Replication Worksheet due Wednesday/Thursday 12/2-12/3/2015 for 15 Points
GRADEBOOK CLOSES FRIDAY 12/11/2015!!!
DNA Structure and Replication Quiz Friday 12/4/2015!!
Steps of DNA Replication• Step 1: Before DNA can replicate, the double helix unwinds.
• An enzyme called “ DNA Helicase” breaks the bonds between the nitrogen bases.• Once the strands separate, proteins prevent the strands from making their
double helix shape.• Areas where the double helix separates are called “Replication forks”.
DNA unwindsDNA Helicase- Enzyme that opens the double helixReplication fork- areas where the DNA opens
Step 1
Steps of DNA Replication• Step 2: At the replication fork, an enzyme known as “DNA
polymerase” moves along each of the DNA strands. • DNA polymerase starts adding nucleotides to the exposed
nitrogen bases; using the base pairing rules. • End result: 2 new double helices are formed.
DNA polymerase: An enzyme adding nucleotides to the EXPOSED bases; forming 2 identical copies of DNA
Step 2Step 1
Steps of DNA Replication• Step 3: Once DNA polymerase adds nucleotides to the exposed bases, it
continues until the polymerase is signaled to detach. • The 2 new double helices are made up of an old and NEW
strand
• DNA sequence is identical to each other and to the original DNA molecule
• End result: 2 identical DNA molecules
• Each made up of an OLD and NEW strand
Step 3