Structure and Organization of DNA Flashcards
Found in conditions of LOW humidity and HIGH salt concentration
A DNA
right handed double helix
MC FORM
Found in conditions of HIGH humidity and LOW salt conditions
highly flexible
B-DNA
Right handed double helix
Phosphodiester backbone assume a zigzag form
Seen in the 5’ end of chromosomes
Z DNA
Left handed DNA
Determine the MELTING point of DNA
check the G-C content
INC G-C content
INC melting point
The most abundant chromatin protein
HISTONES
First level of organization of DNA
2 nm
DNA double helix
Consists of nucleosomes + linker DNA
beads on a string appearance
10 nm chromatin fibril
Group of nucleosomes
30 nm DNA chromatin fibril (solenoid)
Promotes packing of DNA into compact structure
Supercoiled structure
Enzymes that can RELAX or INSERT supercoils
RELIEVE TORSIONAL STRAINS in DNA
Topoisomerase
Make transient SINGLE STRANDED BREAK in an negatively supercoiled DNA double helix
DISRUPTS PHOSPHODIESTER bond
TOPOISOMERASE 1
does NOT need ATP
Dimeric enzyme that bind to DOUBLE STRANDED DNA, make breaks in BOTH STRANDS of DNA
TOPOISOMERASE II
ATP is needed
Chromatin is LESS DENSELY PACKED and STAINS LESS DENSELY
Transcriptionally ACTIVE
EUCHROMATIN
Chromatin is DENSELY PACKED and STAINS DENSELY
Transcriptionally INACTIVE
HETEROCHROMATIN
Always CONDENSED
Essentially INACTIVE
CONSTITUTIVE HETEROCHROMATIN
- centromere
- chromosomal ends of telomere
At times condensed but at other times uncondensed and actively transcribed
one of the x chromosome in mammalian female
heterochromatic x chromosome decondenses during gametogenesis
Central Dogma of Molecular Biology
DNA replication (DNA –> DNA)
Transcription ( DNA –> RNA)
Translation (RNA –> protein)
The COMPLETE set of genes of an organism
GENOME
The complete set of RNA transcripts produced by the genome of an organism
TRANSCRIPTOME
The COMPLETE set of RNA transcripts produced by the genome of an organism
TRANSCRIPTOME
The complete COMPLEMENT of proteins of an organism
PROTEOME
DNA STRUCTURE
All nucleotides are involved in linkage
Antiparallel
Bases are perpendicular to DNA
Attached by hydrogen bond
2 strands of DNA are held together by
Hydrogen Bond
At physiological pH the DNA molecules are
NEGATIVELY CHARGED - d.t. phosphate group
Triplex DNA is d.t.
Hoogsteen pairing
Which model of DNA was discovered by Watson and Crick?
B DNA
Random inactivation of X chromosome
Lyonization
Changes the expression of a DNA segment without changing the sequence
aging, carcinogenesis, genomic imprinting, transposable element repression and inactivation of the X chromosome
DNA METHYLATION
Reversible transcriptional supression
Histone Methylation
Removal of histone’ s (+) charge –> relaxed DNA coiling –> INCREASE TRANSCRIPTION
HISTONE ACETYLATION
Removal of acetyl groups –> tightened DNA coiling –> DECREASE TRANSCRIPTION
HISTONE DEACETYLATION
