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Gain a comprehensive understanding of DNA structure and its impact on protein functions through a mini-lecture and hands-on practice. Explore the surprising discoveries of the Griffith Experiment and DNA structure through informative videos.
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Tuesday, February 6th DNA Structure I can construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life • Today’s agenda: • Warm up • DNA structure mini-lecture • Practice (modeling DNA)
Write down 2 things that surprise you https://www.youtube.com/watch?v=B_PQ8qYtUL0
HOOK http://www.youtube.com/watch?v=1Q67bMYOm7E
Griffith Experiment https://www.youtube.com/watch?v=6j02x67_3jk
Griffith experiment & DNA discovery • Fred Griffith worked with virulent S and nonvirulent R strain Pneumoccocus bacteria • He found that R strain could become virulent when it took in DNA from heat-killed S strain • Study suggested that DNA was probably the genetic material https://www.youtube.com/watch?v=6j02x67_3jk
DNA, Deoxyribonucleic Acid All cells contain DNA which is the genetic material
DNA Structure What are the monomers of nucleic acids?
DNA • Made up of subunits called nucleotides • Nucleotide are made of: 1. Phosphate group 2. 5-carbon sugar 3. Nitrogenous base
Nucleotides Phosphate Nitrogenous Base Sugar Deoxyribose sugar
There are four nitrogen containing bases A T C Adenine Thymine G Guanine Cytosine
A or G T or C Nitrogenous Bases • Double ring PURINES Adenine (A) Guanine (G) • Single ring PYRIMIDINES Thymine (T) Cytosine (C)
C T A G Chargaff’s Rule • Adeninemust pair with Thymine • Guanine must pair with Cytosine
“Rungs of ladder” Nitrogenous Base (A,T,G or C) “Legs of ladder” Phosphate & Sugar Backbone DNA Double Helix
Rule of base pairing Also known as Chargaff’s rule: in a body or somatic cell: A = 30.3% T = 30.3% G = 19.5% C = 19.5%
Check for understanding A segment of DNA has 120 Adenine and 120 Cytosine bases. What’s the total number of nucleotides present in the segment?
Check for understanding A segment of DNA has 120 Adenine and 120 Cytosine bases. What’s the total number of nucleotides present in the segment?
Check for understanding In humans there is approximately 30% adenine, what is the percentage of other nitrogen bases?
Check for understanding In humans there is approximately 30% adenine, what is the percentage of other nitrogen bases?
Check for understanding In DNA guanine is 10%, what is the percentage of adenine?
Check for understanding In DNA guanine is 10%, what is the percentage of adenine?
Discovery of DNA • Rosalind Franklin took diffraction x-ray photographs of DNA crystals • In the 1950’s, Watson & Crick built the first model of DNA using Franklin’s x-rays
Rosalind Franklin https://www.youtube.com/watch?v=JiME-W58KpU