DNA

Characteristics of DNA 1. Supplies instructions for cell processes, like how to make proteins 2. Can be copied each time a cell divides 3. It is the “blueprint of life”, every living thing has DNA

DNA Structure Is a nucleic acid that is double stranded Made up of subunits called nucleotides

A nucleotide consists of 3 parts: 1. Phosphate 2. Sugar 3. Nitrogen base: adenine (A), guanine (G), thymine (T), cytosine (C) Base (A, T, G, C) Sugar Phosphate

Hydrogen bonds Nucleotide Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Structure of DNA Section 12-1

Finding DNA’s Shape: the Double Helix Scientific Contributions: 1. Rosalind Franklin: showed DNA was a spiral shape by using X rays 2. Chargaff’s rule: A pairs with T, G pairs with C One strand reads: T C G A A C T The other reads: AAGTTCG

Scientific Contributions Cont. 3. Watson and Crick: made a model of DNA structure in 1953 The “Double Helix” looks like a twisted ladder Sides of the ladder are alternating sugar and phosphate units Rungs are the bases held together by hydrogen bonds

DNA Replication Def: Ability of DNA to make an exact copy or a new strand of DNA from an old one

The Steps in Replication 1. Start with a DNA molecule 2. Hydrogen bonds break and the strands separate (unzip) 3. Add matching nucleotides 4. The result: 2 identical DNA molecules ½ old strand, ½ new strand

Drawing DNA Replication: Step 1

Drawing DNA Replication: Steps 2 and 3

Drawing DNA Replication: Step 4

DNA Replication:

Chromosomes Tight coils and supercoils of DNA and protein

Chromosome Supercoils Coils Nucleosome Histones DNA double helix Section 12-2

Chromosome Supercoils Coils Nucleosome Histones DNA double helix Section 12-2

Chromosome Supercoils Coils Nucleosome Histones DNA double helix Section 12-2

Chromosome Supercoils Coils Nucleosome Histones DNA double helix Section 12-2

Chromosome Supercoils Coils Nucleosome DNA double helix Section 12-2