DNA Structure
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DNA Structure
Unit 2-1 NotesMr. Hefti – Pulaski Biology
What are these?
What is this?
How are they related? [similar in
shape]
How are they related?
What is this?
[both contain instructi ons]
What is this?
A. DNA = blueprint for life• All living things possess DNA• Located in the nucleus• Chemical instructions for structure
and function• Unique code tells cells what to do
B. DNA is a “double helix”• Think - twisted ladder• There’s a left and right side
chemically bonded together in the middle • Held together by hydrogen bonds
C. DNA made of repeating units called nucleotides
• Here are the 3 parts of a nucleotide:
(please draw in notes)
D. Phosphate• Made of H, O and P• Phosphate links nucleotides together
E. Deoxyribose sugar
• 5 carbon sugar (pentagon shaped)• Made of C, H and O• Deoxyribose links phosphate and nitrogenous
base
F. Nitrogenous base
• Made up of C, H, O and N• Form rungs of ladder• 4 types:– Adenine (A)– Thymine (T)– Guanine (G)– Cytosine (C)
G. Base-pairing rules
• A always pairs with T• C always pairs with G
H. In conclusion…
• The combination of As, Ts, Cs, and Gs is what makes each organism unique• Human DNA composed of 3 billion
repetitions of those same 4 letters
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