Chapter 2 DNA Structure I genetics Book

7/28/2019 Chapter 2 DNA Structure I genetics Book

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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

Chapter 2 DNA Structure I genetics Book

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