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Chapter 2DNA: The Genetic Material
Copyright 2010 Pearson Education Inc.
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Gregor Mendel
Factors of heredity
Scientists prior to Mendel
Seeds of heredity Key characteristics of the genetic material
Contain a stable form of the information about
the cell structure, function, development, and
reproduction of an organism Accurate replication
Capable of change
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Friedrich Miescher (1869)
Discovery of nucleic acid
Isolation of a substance from pus which
contained CHONP Later found in the nuclei of all biological samples
studied
Called nuclein
ca. 1900 Discovery of chromosomes
Composed of protein and nucleic acids
Are the molecules of heredity
Which of these is the molecule of heredity?
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Streptococcus pneumoniae
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Conclusion
Somehow interaction among the two strains
allowed for the transformation
Genetic material from the S strain incorporatedinto de the genetic material of the R strain
Transforming principle
It might be protein (supposition)
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Used IIIS and IIR bacteria
Lysed IIIS and made extracts
Incubated extracts with IIR bacteria and
plated Transformation occurred to IIIS bacteria
Conclusion?
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Used IIIS and IIR bacteria
Lysed IIIS and made extracts
Incubated extracts with enzymes to degrade
each one of the macromolecules Incubated treated extracts with IIR bacteria
and plated
Transformation occurred to IIIS bacteria only
when DNA was not degraded
Conclusion?
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Only viruses
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Polymers vs.
monomers
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Helical structure
Two regularities
0.34 nm
3.4 nm 2 nm diameter
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Types of RNA
mRNA
tRNA
rRNA snRNA
miRNA
Configuration of RNA
ssRNA dsRNA
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Viral genomes
Prokaryotic genomes
Eukaryotic genomes
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DNA
Double stranded or single stranded or mixture
Circular or linear
Single or fragmented
RNA
Double stranded or single stranded
Circular or linear Single or fragmented
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Most Single
Double stranded
Circular
Organized in a nucleoid
Some Multiple
Linear or circular
Smaller autonomously-replicatingchromosomes not essential to the life of thecell Plasmids
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Borrelia burgdorferi 0.91 Mb linear chromosome
17 plasmids some linear, some circular with acombined size of 0.53 Mb
Rhizobium radiobacter 3 Mb circular chromosome
2.1 Mb linear chromosome
Methanococcus jannaschii 1.66 Mb circular chromosome
58 kb & 16 kb circular plasmids
Archaeoglobus fulgidus Single 2.2 Mb circular chromosome
Escherichia coli Single 4.6 Mb circular chromosome
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Topoisomerases
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Multiple
Linear
Terms
Karyotype complete set of metaphasechromosomes in a eukaryotic cell
C-value amount of DNA in the haploid genome
Species specific
Chromosomes in the cell cycle
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Chromatin stainable material in the cell
nucleus
DNA
Protein
Histones
H1, H2A, H2B, H3, H4
Non-histones
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Solenoid model
Zigzag model
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Figure 4-32 Molecular Biology of the Cell( Garland Science 2008)
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Figure 4-31 Molecular Biology of the Cell( Garland Science 2008)
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Euchromatin
Actively transcribed
Devoid of repetitive sequences
Heterochromatin
transcriptionally inactive Constitutive
Identical positions in both homologs and consists
mainly of repetitive sequences
Centromeres, telomeres
Facultative
Differs depending of the stage and can be different in
different homologs
Represents condensed euchromatin
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Centromere CEN region in yeast
S. cerevisiae
Centromeres in
individualchromosomes aredifferent 112 120 bp
CDEII 78 86 bp >
90% A-T CDEI 8 bp RTCACRTG
CDEIII 26 bp A-T rich
Telomere 100 1000 copies
Simple telomericsequences Repetitive sequences Tandemly repeated
DNA sequences
Tetrahymena5-TTGGGG-3
Homo sapiens 5-TTAGGG-3
Telomere-associatedsequences
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Unique-sequence DNA
One to few copies in the genome
All of the genome in prokaryotes and some
present in eukaryotes (55-60% in humans)
Most protein-coding gene regions
Moderately repetitive DNA
Few to 105 copies in the genome
Present in eukaryotesHighly repetitive DNA
105 to 107 copies in the genome
Present in eukaryotes
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Dispersed repeated DNA
Long-interspersed elements (LINEs)
1000 7000 bp
Short-interspersed elements
100 400 bp (SINEs)
Tandemly repeated DNA
1 10 bp
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