Genes and Chromosomes

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Chapter 24 Genes and Chromosomes
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BMSE SeminarFriday May 4, 2007 300pm Webb
1100NAGARAJAN VAIDEHIImmunology DivisionCity
of HopeStructure, Function, and Conformation
Flexibility of G-protein coupled Receptors
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James Thomson, Ph.D.John D. MacArthur Professor
of Anatomy, University of WisconsinSelf-renewal
and early differentiation of human ES
cellsTuesday, May 1, 2007, 330 pmRathmann
Auditorium1001 Life Science Building
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Frontiers in Cancer Research Special Lecture
SeriesTuesday May 1, 2007 630pmTheatre and
Dance Bldg, Rm 1701JAMES THOMSON Human
Embryonic Stem Cells Implications for Basic
Cancer Research
MCDB SeminarThursday May 3, 2007330pmLSB 1001
MARTIN SAGERMANNDesigning Protein Functions
for Novel Applications
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• 24.1 chromosomal elements
• Genes? RN A?proteins
• Lengths of DNA
• Eurkaroytic genes are complex

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Packaging problem T2 bacteriophage (single
linear DNA) Bacteria Eukaryote (human).
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Phenotype Regulatory sequences Beginning, end,
transcriptional regulation, splicing variants
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Compare to bacteriamultiples of 106
bp eukaryotesmultiples of 109 bp
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Escherichia coli (E. coli) has 4.6 million bp and
approximately 4,200 genes P. Aeruginosa has more
than 6 million bp and approximately 5,500 genes
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Diploid/haploid 22 chromosomes plus 2Xs or X and
Y Human1014 cells and 1011 km of DNA vs earth
circumference4 x 104 km
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Introns, exons, eukaryotic genes
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Long interspersed elements (6-8 kbp) Short
interspersed elements (100-300 bp) Alu elements
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Yeast chromosome Centromere100 bpbut much
larger in higher eukaryotes Telemomeresrepeats
of (TxGy)nyeast n 100, higher are 1500 or so
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24.2 Supercoiling

• Cellular DNA is underwound
• Topological linkage number
• Topoisomerase
• DNA compaction

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Plasmid, electron micrograph.
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Linkage number (Lk)topology, dsDNA, remains
unchanged unless strands are broken.
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Lk Tw Wr (twist and writhe)
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Treatment with Topoisomerase I
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Topoisomerases change linkage number
(I,II) Replication, DNA packaging Iincrements of
1 IIincrements of 2
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Type II topoisomerase mechanism 2 ATP consumed
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The need for greater compaction of DNA in
bacteriaplectonemic (twisted) and solenoidal
supercoiling
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Right handed supercoils in underwound
(negatively supercoiled DNA)
Tight left handed turns
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24.3 Chromosomal structure
Chromatin Histones Nucleosomes Condensed
chromosomes
Changes in chromosomes during eukaryotic cell
cycle
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Histones small (11-21 Kd), positively charged
(Arg, Lys), highly conserved proteins
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Repeating 200 bp of DNA (146 bp tightly wrapped)
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Higher order organization of nucleosomes, 30 nm
fiber
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Higher order human DNA packing.
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Bacteria use proteins to compact their
DNAnucleoids