Chapter 7

Molecular organisationMolecular organisationof chromosomes

OverviewIntroductionGenome sizeDNA supercoilingBacterial chromosomesEukaryotic chromosomesPolytene chromosomesPolytene chromosomesUnique and repetitive sequences in eukaryotesMolecular structure of the centromereMolecular structure of the centromereMolecura structure of the telomere

Introduction

Chrom. Prokaryotes EukaryotesNumbers Usually 1 Usually > 1Shape Usually Usually linearShape Usually

circularUsually linear

Location Free NucleusLocation Free NucleusExtra Plasmids Mitochondria

Chl l tChloroplasts

OverviewIntroductionGenome sizeDNA supercoilingBacterial chromosomesEukaryotic chromosomesPolytene chromosomesPolytene chromosomesUnique and repetitive sequences in eukaryotesMolecular structure of the centromereMolecular structure of the centromereMolecura structure of the telomere

Genome size and evolutionary ycomplexity: C-value paradox

Genome size and evolutionary ycomplexity: C-value paradox

Genome size and evolutionary ycomplexity: C-value paradox Overview

IntroductionGenome sizeDNA supercoilingBacterial chromosomesEukaryotic chromosomesPolytene chromosomesPolytene chromosomesUnique and repetitive sequences in eukaryotesMolecular structure of the centromereMolecular structure of the centromereMolecura structure of the telomere

The supercoiling of DNAp gDefinition

The supercoiling of DNAp gDefinition

The supercoiling of DNAp gTopoisomerase I

The supercoiling of DNAp gTopoisomerase II

OverviewIntroductionGenome sizeDNA supercoilingBacterial chromosomesEukaryotic chromosomesPolytene chromosomesPolytene chromosomesUnique and repetitive sequences in eukaryotesMolecular structure of the centromereMolecular structure of the centromereMolecura structure of the telomere

The structure of bacterial chromosomes

Packaging proteins:HU (wrapping) FIS & IHF (bending) HU (wrapping), FIS & IHF (bending), HNS (compaction)

NucleoidNucleoidIndependent, supercoiled loops

The structure of bacterial chromosomes Overview

IntroductionGenome sizeDNA supercoilingBacterial chromosomesEukaryotic chromosomesPolytene chromosomesPolytene chromosomesUnique and repetitive sequences in eukaryotesMolecular structure of the centromereMolecular structure of the centromereMolecura structure of the telomere

Eukaryotic chromosomesyPackaging feat

One extended chromosome = 35 Km long 1mm spaghettilong 1mm spaghettiTo organize in nucleus = boxTo organize in metaphase chromosome: 16 x 2 feet canoe

Eukaryotic chromosomesyChromatin & the nucleosome

Chromatin = DNA + proteins (histone + non-histone))Nucleosome

Core particle (145 bp + 2x Core particle (145 bp + 2x [H2A,H2B,H4,H4]+ linker DNA + H1

Histones:Rich in ARG and LYSRich in ARG and LYSHighly conservedModified histone NH2-tailsModified histone NH2-tails

Eukaryotic chromosomesyThe nucleosome

Eukaryotic chromosomesyThe nucleosome

Eukaryotic chromosomesyThe nucleosome

Eukaryotic chromosomesy30nm fiber

Eukaryotic chromosomesyChromosome territories

Eukaryotic chromosomesyCondensation at cell division

CondensinsCondensins

Eukaryotic chromosomesyCondensation at cell division

ChromosomeChromosomescaffold

OverviewIntroductionGenome sizeDNA supercoilingBacterial chromosomesEukaryotic chromosomesPolytene chromosomesPolytene chromosomesUnique and repetitive sequences in eukaryotesMolecular structure of the centromereMolecular structure of the centromereMolecura structure of the telomere

Giant polytene chromosomes OverviewIntroductionGenome sizeDNA supercoilingBacterial chromosomesEukaryotic chromosomesPolytene chromosomesPolytene chromosomesUnique and repetitive sequences in eukaryotesMolecular structure of the centromereMolecular structure of the centromereMolecura structure of the telomere

Unique & repetitive sequences q p qRenaturation kinetics

Unique & repetitive sequences q p qRenaturation kinetics

Highly repetitiveg y p

Middle repetitiveMiddle repetitive

Unique

Unique & repetitive sequencesq p qHighly repetitive sequences

Localized “satellite” repeats = heterochromatin

Unique & repetitive sequencesq p qHighly repetitive sequences

Interspersed repeats

Unique & repetitive sequencesq p qMiddle repetitive sequences

Less abundant transposonsPseudogenesPseudogenesGene familiesSegmental duplications

Unique & repetitive sequencesq p qUnique sequences

GenesRegulatory elementsRegulatory elements

OverviewIntroductionGenome sizeDNA supercoilingBacterial chromosomesEukaryotic chromosomesPolytene chromosomesPolytene chromosomesUnique and repetitive sequences in eukaryotesMolecular structure of the centromereMolecular structure of the centromereMolecura structure of the telomere

Molecular structure of the centromereMolecular structure of the centromereTypes

Holocentric chromosomes (f.i. C. elegans)elegans)Localized centromeres

P i (f i S i i )Point centromeres (f.i. S. cerevisiae)Regional centromeres (f.i. mammals)

Molecular structure of the centromereMolecular structure of the centromerePoint centromeres

Molecular structure of the centromereMolecular structure of the centromereRegional centromeres

OverviewIntroductionGenome sizeDNA supercoilingBacterial chromosomesEukaryotic chromosomesPolytene chromosomesPolytene chromosomesUnique and repetitive sequences in eukaryotesMolecular structure of the centromereMolecular structure of the centromereMolecular structure of the telomere

Molecular structure of the telomereMolecular structure of the telomereFunction of telomerase

Molecular structure of the telomereMolecular structure of the telomereFunction of telomerase

Molecular structure of the telomereMolecular structure of the telomereTelomerase

Molecular structure of the telomereMolecular structure of the telomereTelomeric DNA

Molecular structure of the telomereMolecular structure of the telomereG-quartet structure