Download 12-2 Chromosomes and DNA Replication

Chapter 12: DNA and RNA (12-2)
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Prokaryotes—DNA in a circular from (plasmid)
Eukaryotes—much more complicated
Chromosome Structure
 Eukaryotic DNA is tightly packed
 Smallest chromosome contains 30 million base
pairs.
 Chromatin—DNA and Proteins
 The DNA is coiled around proteins called histones.
 DNA + histones = nucleosome
o coiled and coiled…super coiled!!!!
Chapter 12: DNA and RNA (12-2)
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The structure of DNA explains how it can be
copied—base pairing (A-T, C-G)
Complimentary strands
Before cell division, the DNA must be replicated
During DNA replication the DNA molecule
separates into two strands, then produces 2 new
complimentary strands following the rules of base
pairing. Each strand of the double helix of DNA
serves as a template, or model, for the new strand.
Controlled by enzymes
enzymes “unzip” a molecule of DNA…breaking
hydrogen bonds
Each strand serves as a template for the attachment
of complimentary bases
DNA molecules consist of one old and one new
strand—semi conservative.
DNA polymeraseconstructs the DNA and
“proofreads.”