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Copyright © 2009 Pearson Education, Inc.
Chapter 12DNA Organization in
Chromosomes
Copyright © 2009 Pearson Education, Inc.
Copyright © 2009 Pearson Education, Inc.
• Single nucleic acid molecule
• No proteins
• DNA or RNA
• Single or double stranded
• Circular or linear
• Packed into a small volume
Viral Genetic Material
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• Single nucleic acid molecule
• Some proteins
• Always double stranded DNA
• Large, circular chromosome
• Packed into a small volume (nucleoid region)
Bacterial Genetic Material
Copyright © 2009 Pearson Education, Inc. Table 12.1
Copyright © 2009 Pearson Education, Inc. Figure 12.2
Copyright © 2009 Pearson Education, Inc. Figure 12.3
Copyright © 2009 Pearson Education, Inc. Figure 12.4
Supercoiling
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• Polytene chromosomes
• Lamp brush chromosomes
Specialized Eukaryotic Chromosome Organizations
Copyright © 2009 Pearson Education, Inc. Figure 12.5
Polytene
Copyright © 2009 Pearson Education, Inc. Figure 12.6
Polytene
Copyright © 2009 Pearson Education, Inc. Figure 12.7
Lamp Brush
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• Only visible during mitosis
• Easier to move DNA around
• Normally uncoiled and dispersed
• Chromatin
• Available for genetic activity
Eukaryotic Chromosomes
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• DNA has a substantial amount of associated proteins
• Histones
• Non-histones
Chromatin
Copyright © 2009 Pearson Education, Inc. Table 12.2
Copyright © 2009 Pearson Education, Inc. Figure 12.8
Copyright © 2009 Pearson Education, Inc. Figure 12.9
Copyright © 2009 Pearson Education, Inc.
• Highly folded DNA presents a problem – genes are inaccessible
• High resolution images showed how chromatin could be remodeled
• Histone tails
• Remodeling
• Acetylations
• Methylation
• Phosphorylation
Chromatin Remodeling
Copyright © 2009 Pearson Education, Inc. Figure 12.10
Copyright © 2009 Pearson Education, Inc.
• Euchromatin
• Light staining
• Active genes
• Uncoiled during interphase
• Heterochromatin
• Heavy staining
• No (few) active genes
• Tightly packed during interphase
Euchromatin vs Heterochromatin
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• Enabled further characterization of chromosomes (previously only size)
• C – banding
• Centromeres stain darkly
• G – banding
• Digest with trypsin before staining
Banding Patterns
Copyright © 2009 Pearson Education, Inc. Figure 12.11
C – Banding
Copyright © 2009 Pearson Education, Inc. Figure 12.12
G – Banding
Copyright © 2009 Pearson Education, Inc. Figure 12.13
X chromosome banding pattern
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• Satellite DNA
• Centromeric sequences
• Telomeric sequences
• Middle (moderate) repetitive DNA
• VNTRs
• STRs
• Transposable sequences
• Pseudogenes
Repetitive Sequences
Copyright © 2009 Pearson Education, Inc. Figure 12.15
Satellite DNA
Copyright © 2009 Pearson Education, Inc. Figure 12.16
Satellite DNA
Copyright © 2009 Pearson Education, Inc. Figure 12.17
Centromeric Sequences
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