1. Structure of DNASection12.2

Components of DNA

DNA (deoxyribonucleic acid) is a nucleic acid made up of nucleotides joined into long strands by covalent bonds

Nucleotides

Nucleotides are building blocks of nucleic acids Nucleotides: 3 parts▪ 5-carbon sugar: deoxyribose▪ Phosphate group▪ Nitrogenous base

▪ 4 Nitrogenous bases (contain Nitrogen): Adenine Guanine Thymine Cytosine

Bonds

Nucleotides joined by covalent bonds Forms between sugar of one nucleotide and

phosphate group of the next.

Nitrogenous bases-Stick out sideways from the nucleotide chain -Nucleotides can be joined together in a number of different ways-Any base sequence is possible-That’s what makes us so different!-Have a special chemical structure that is especially good at absorbing UV light

Stop and Write(2-5 min.)

1. What are the 3 components of a nucleotide?

2. What are the four nitrogenous bases?

3. Do you think excessive UV light could damage your DNA? How?

Erwin Chargaff

Austrian-American biochemist Discovered that % of:

Adenine [A]= Thymine [T] Guanine[G]= Cytosine [C]

P. 345 Analyzing data #1-4 (5 min.)

2. Double- helix

Explains Chargaff’s rule Antiparallel strands

DNA runs in opposite directions Hydrogen bonds

- Both strands of DNA are held together by H bonds between nitrogenous bases (A and T) and (G and C).

-Base pairing-A always lines up perfectly with T -G always lines up perfectly with C

Structure Review

Photo credits

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