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Chapter 7 Molecular Organization of Chromosomes. The range of genome sizes in the animal & plant kingdoms. DNA can assume alternative conformations such as partially melted or supercoiled states. Mechanism of action of a topoisomerase. Mechanism of folding of a bacterial chromosome. - PowerPoint PPT Presentation
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Chapter 7Chapter 7
Molecular Organization of Molecular Organization of ChromosomesChromosomes
The range of genome sizes The range of genome sizes in the animal & plant kingdomsin the animal & plant kingdoms
DNA can assume alternative conformations DNA can assume alternative conformations such as partially melted or supercoiled such as partially melted or supercoiled
statesstates
Mechanism of action of a Mechanism of action of a topoisomerasetopoisomerase
Mechanism of folding of a bacterial Mechanism of folding of a bacterial chromosomechromosome
There are many supercoiled loops (~100 in E. coli) attached to a central core. Each loop can be independently relaxed or condensed.
Packing of DNA in an eukaryotic cell involves wrapping Packing of DNA in an eukaryotic cell involves wrapping around a core of basic (positively charged) proteins called around a core of basic (positively charged) proteins called
histoneshistones
Steps in the folding of DNA Steps in the folding of DNA to create an eukaryotic chromosometo create an eukaryotic chromosome
The rate of renaturation of single stranded DNA The rate of renaturation of single stranded DNA depends upon the concentration and sequence complexitydepends upon the concentration and sequence complexity
The rates of renaturation of DNAs The rates of renaturation of DNAs with different kinetic complexitieswith different kinetic complexities
DNA of an eukaryotic cell has several DNA of an eukaryotic cell has several components components
with different kinetic complexitieswith different kinetic complexities
DNA with low kinetic complexity is located in the DNA with low kinetic complexity is located in the middle (near the centromere) and at the endsmiddle (near the centromere) and at the ends
(near the telomeres) of a chromosome (near the telomeres) of a chromosome
Structure of the centromere Structure of the centromere in a in a
SaccharomycesSaccharomyces chromosome chromosome
The centromere DNA has 4 centromere determining
elements (CDEs)
Replication of telomere DNA repeatsReplication of telomere DNA repeats
Mechanism of replication of telomere Mechanism of replication of telomere DNA DNA
by the enzyme telomeraseby the enzyme telomerase
The enzyme telomerase has a
RNA molecule that serves as the template
for telomere DNA synthesis.
Telomerase has protein and Telomerase has protein and RNA componentsRNA components
Proposed 4-stranded structure of Proposed 4-stranded structure of telomere DNA telomere DNA
in two protozoansin two protozoans
Hydrogen bonding Hydrogen bonding structure of G quartetstructure of G quartet