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Nucleic Acid Structure and
Organization
Asmarinah
Department of Medical Biology
Nucleic acid
- Macromolecules consisting of a chain of
nucleotides joined together by phosphodiester
bonds
- divided into:
DNA (Deoxyribonucleic acid) molecules
RNA (Ribonucleic acid) molecules
DNA and its building
DNA is made from subunits, called nucleotides
Each nucleotide consisting of
-Sugar (deoxyribose)
-Phosphate
-Base: Adenine
Thymine
Guanine
Cytosine
DNA - Gene
A gene is defined as a segment of DNA that contains the
insctruction for making a particular protein
● DNA molecules are organized into chromosome
● Chromosome: A DNA molecule with its attendant
proteins that moves as an independent units during
mitosis and meiosis
Before DNA replication, each chromosome consists of a
single DNA molecule plus protein, is called a chromatid
After replication, each chromosome consists of two
identical DNA molecule plus proteins; this are called
sister chromatids
● Chromatin: DNA plus the proteins that package it
within the cell nucleus
A
B
C
A. The principal structural features of chromosome
B. An electron micrograph of human mitotic
chromosomes
C. A diagram of various classes of human chromosomes
Chromatin packing
occurs on several levels
Structural organization
of nucleosome
Nucleosome contains
Octameric histon protein &
DNA double helix
Genome
The totality of genetic information belonging to a
cell or an organism; in particular, the DNA that
carries this information
Genomics
The science of studying the DNA sequences
and properties of entire genomes
Human Genome
Each human chromosome
has a unique banding
pattern
The Organization of human genome
Conserved gene order in chromosome between the
human (a) and mouse (b) genome
Closely related species can have very different
chromosome numbers
Chromosomes from many eucaryotes (including human)
contain a large excess of interspersed DNA that does not
seem to carry critical information, called junk DNA
This DNA may not be important, but can play a role:
- as spacer material
- for long-term evolution of the species
- for the proper expression of genes
Bacteria and some single-celled eucaryotes have especially
compact genomes. The complete nucleotide sequence of
their genomes reveals that DNA molecules are little more
than strings of closely packed genes
Mitochondrial DNA
Chromosome No. 25
 Genome  circular double
stranded DNA
 Maternal inherited
 Mito DNA : 16.569 bp
Nuclear DNA : 3 x 109 bp

The structure of mitochondria
- contains two membranes:
* outer mitochondrial membrane
* inner mitochondrial membrane
-There is two aqueous compartment:
* Matrix, within the interior
* Intermembrane space, between
OMM and IMM
Role of mitochondria
produce ATP
5 respiration enzyme complexes
complex I (NADH oxydoreductase : Ubiquinone)
complex II (suksinat oxydoreductase : ubiquinone)
complex III (ubiquinol oxydoreductase : sitokrom c)
complex IV (Cytocrome c oxydase)
complex V (ATPsynthase).
The genome of E. coli
A. E.coli strain K-12 has 4.639.221
nucleotides pairs
B. A diagram of the E. coli genome.
E. Coli genome is circular that forms
a single, closed loop.
Yellow or orange bars shows
protein-coding genes
Green arrows indicate genes
encoding only RNA molecules
Genetic differences between pathogen and
nonpathogen bacteria
Example: Genetic organization of Vibrio cholerae
A. Vibrio cholerae has two circular
chromosomes, that each of its has
distinct origin of replication (oriC1 &
oriC2)
CTXφ locus carriers the gene
for cholera toxin
VPI island contains gene for
factors required for intestinal
colonization
B. Map of CTXφ locus consist of: - core region: gene for cholera toxin ctxA & ctxB
gene for involving of virulence (ace & zot)
- repeated sequence RS2 & RS1 that involved
chromosomal insertion of bacteriophage genome
Schematic drawings of several types of viral
genomes
RNA
Polymer formed from covalently linked
ribonucleotide monomer
Type of RNA:
-mRNA = messenger RNA, code for protein
-rRNA = ribosomal RNA, form basic structure
of ribosome and catalyze protein synthesis
-tRNA = tranfer RNA, central to protein
synthesis as adaptors between mRNA and
amino acids
-snRNA = small nuclear RNA, function an variety of
nuclear process
-snoRNA = small nucleolar RNA, used to process and
chemically modify rRNA
-scaRNA = small cajal RNA, used to modify snoRNA and
snRNA
-miRNA = microRNA, regulate gene expression typically
by blocking translation of selective mRNA
-siRNA = small interfering RNA, turn off gene expression
by directing degradation of selective mRNA and the
establishment of compact chromatin structure
mRNA
References:
-Albert et al., 2008. Molecular biology of the cell.
5th ed.
-Albert et al., 2004. Essential of cell biology.
-Pollard and Earnshaw. 2004. Cell biology.