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http://upload.wikimedia.org/wikipedia/commons/f/f0/DNA_Overview.png8/12/2019 DNA Technology Lect 1
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Deoxyribonucleic acid(DNA)is a nucleic acidthat
contains the geneticinstructions used in the development
and functioning of all known living organisms.
The main role of DNA moleculesis the long-term storage
of information.
DNA contains the instructions needed to construct other
components of cells, such as proteins and RNA
molecules.
http://en.wikipedia.org/wiki/Nucleic_acidhttp://en.wikipedia.org/wiki/Geneticshttp://en.wikipedia.org/wiki/Developmental_biologyhttp://en.wikipedia.org/wiki/Lifehttp://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Informationhttp://en.wikipedia.org/wiki/Cell_%28biology%29http://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/RNAhttp://en.wikipedia.org/wiki/RNAhttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Cell_%28biology%29http://en.wikipedia.org/wiki/Informationhttp://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Lifehttp://en.wikipedia.org/wiki/Developmental_biologyhttp://en.wikipedia.org/wiki/Geneticshttp://en.wikipedia.org/wiki/Nucleic_acid8/12/2019 DNA Technology Lect 1
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The DNA segments that carry this genetic information are
called genes, but other DNA sequences have structural
purposes, or are involved in regulating the use of this genetic
information.
This information is read using the genetic code, which
specifies the sequence of the amino acidswithin proteins.
The code is read by copying stretches of DNA into the
related nucleic acid RNA, in a process called transcription.
http://en.wikipedia.org/wiki/Genehttp://en.wikipedia.org/wiki/Genetic_codehttp://en.wikipedia.org/wiki/Amino_acidhttp://en.wikipedia.org/wiki/Transcription_%28genetics%29http://en.wikipedia.org/wiki/Transcription_%28genetics%29http://en.wikipedia.org/wiki/Amino_acidhttp://en.wikipedia.org/wiki/Genetic_codehttp://en.wikipedia.org/wiki/Gene8/12/2019 DNA Technology Lect 1
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Attached to each sugar is one of four types of molecules
called bases. It is the sequence of these four bases along
the backbone that encodes information.
Within cells, DNA is organized into structures called
chromosomes. These chromosomes are duplicated beforecells divide, in a process called DNA replication.
Chemically,DNA is a long polymerof simple units called
nucleotides, with a backbone made of sugars and
phosphate groups joined by esterbonds.
http://en.wikipedia.org/wiki/Nucleobasehttp://en.wikipedia.org/wiki/Chromosomehttp://en.wikipedia.org/wiki/Cell_divisionhttp://en.wikipedia.org/wiki/DNA_replicationhttp://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Nucleotidehttp://en.wikipedia.org/wiki/Esterhttp://en.wikipedia.org/wiki/Esterhttp://en.wikipedia.org/wiki/Nucleotidehttp://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/DNA_replicationhttp://en.wikipedia.org/wiki/Cell_divisionhttp://en.wikipedia.org/wiki/Chromosomehttp://en.wikipedia.org/wiki/Nucleobase8/12/2019 DNA Technology Lect 1
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Eukaryotic organisms such as animals, plants, and
fungistore their DNA inside the cell nucleus.
In prokaryotic organisms such as bacteria DNA is
found in the cell's cytoplasm.
Within the chromosomes, chromatinproteins such ashistones compact and organize DNA. These compact
structures guide the interactions between DNA and other
proteins, helping control which parts of the DNA are
transcribed.
http://en.wikipedia.org/wiki/Eukaryotehttp://en.wikipedia.org/wiki/Animalhttp://en.wikipedia.org/wiki/Planthttp://en.wikipedia.org/wiki/Fungushttp://en.wikipedia.org/wiki/Cell_nucleushttp://en.wikipedia.org/wiki/Bacteriahttp://en.wikipedia.org/wiki/Cytoplasmhttp://en.wikipedia.org/wiki/Chromatinhttp://en.wikipedia.org/wiki/Histonehttp://en.wikipedia.org/wiki/Histonehttp://en.wikipedia.org/wiki/Chromatinhttp://en.wikipedia.org/wiki/Cytoplasmhttp://en.wikipedia.org/wiki/Bacteriahttp://en.wikipedia.org/wiki/Cell_nucleushttp://en.wikipedia.org/wiki/Cell_nucleushttp://en.wikipedia.org/wiki/Cell_nucleushttp://en.wikipedia.org/wiki/Fungushttp://en.wikipedia.org/wiki/Planthttp://en.wikipedia.org/wiki/Animalhttp://en.wikipedia.org/wiki/Eukaryotehttp://en.wikipedia.org/wiki/Eukaryotehttp://en.wikipedia.org/wiki/Eukaryote8/12/2019 DNA Technology Lect 1
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Structure of DNA
Four different deoxynucleotides, the structural units of DNA,
areassembled into long polymers of DNA strands.
Prior to assembly, they are in the form of nucleotide
triphosphates similar to ATP and linked together by
phosphodiester bond.
Each nucleotide contains three parts: a phosphate group,
the sugar deoxyribose and one of four nitrogen bases.
The four bases of DNA, their designations and their
triphosphate form are adenine (dATP), guanine(dGTP),
thymine (dTTP), and cytosine (dCTP).
http://www.accessexcellence.org/AB/GG/dna_molecule.htmlhttp://www.encyclopedia.com/printablenew/20005.htmlhttp://www.encyclopedia.com/printablenew/20005.htmlhttp://www.accessexcellence.org/AB/GG/dna_molecule.html8/12/2019 DNA Technology Lect 1
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Nitrogenous bases of DNA molecule
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DNA Deoxynucleotide
Cytosine
Deoxyribose
Phosphate
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nucleoside
nucleotide
deoxy nucleotide
Ribose
Deoxyr ibose
Three-dimension structure
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Chargaffdeveloped the principle of base-pairing. He
determined the relative amounts of A, T, C, and G in a
variety of cells, proving that A = T and C = G and thatthere is exactly as much purine (adenine and guanine)
in the nucleus as there is pyrimidine (thymine and
cytosine).
Through the use of X-ray crystallography, Wilkins and
Franklindetermined that DNA was double stranded and
could form a helix.
http://helix.biology.mcmaster.ca/721/outline2/node57.htmlhttp://www.ultranet.com/~jkimball/BiologyPages/B/BasePairing.htmlhttp://www-structure.llnl.gov/Xray/101index.htmlhttp://www.pbs.org/wgbh/aso/databank/entries/bofran.htmlhttp://www.pbs.org/wgbh/aso/databank/entries/bofran.htmlhttp://www-structure.llnl.gov/Xray/101index.htmlhttp://www-structure.llnl.gov/Xray/101index.htmlhttp://www-structure.llnl.gov/Xray/101index.htmlhttp://www.ultranet.com/~jkimball/BiologyPages/B/BasePairing.htmlhttp://www.ultranet.com/~jkimball/BiologyPages/B/BasePairing.htmlhttp://www.ultranet.com/~jkimball/BiologyPages/B/BasePairing.htmlhttp://helix.biology.mcmaster.ca/721/outline2/node57.html8/12/2019 DNA Technology Lect 1
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Primary structure of DNA
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2 chains
purine opposite a pyrimidine
chains held together by H-bonds
Guanine is paired with cytosine by three H-bondsAdenine is paired with thymine by two H-bonds
anti-parallel orientation of the two chains
5'--------------->3
3'
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Forms of DNA
B-form DNA
In this conformation, the backbone traces a r ight handed
helix, each turn of which contains 10 nucleotides. This is
the most popular double-helix conformation.
Z-form DNA
DNA is also capable of twisting to the left.
In this form, the phosphate groups trace a zigzagpattern.
Thus the transition between the two forms might act like a gene swi tch
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B-Form Z-Form
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The main DNA in p rokaryo tes is a circular molecule attached to
the plasma memb rane.
Some DNA is o rganized in smal ler circles cal led plasmid s.
90% of the genome cons ists o f fun ct ion al genes, i .e. genes
coding fo r proteins invo lved in DNA repl icat ion and DNA
transcr ip t ion only.
Prokaryot ic DNA
Eukaryot ic DNA
In eukaryotes, DNA is assoc iated with p roteins to fo rm acom plex cal led chromatin, th is structure al lows num erous
con f igurat ions o f the DNA mo lecu le.
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Chromatin consists of:
1-Very long double-stranded DNA molecule
2-A nearly equal mass of:
a-small basic proteins called histones
b-non-histone proteins (acidic proteins and larger than histones),
they include: enzymes involved in DNA replication such as DNA
topoisomeraseand proteins involved in transcription such as the
RNA polymerase complex
c-a small quantity of RNA
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Non-histones are regulatory proteins,
e.g. leucine zippers; zinc fingers.
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Frederick Griffithfound that Streptococcu s pneumoniae
bacterium had two forms when grown on agar plates, a
smooth (S)and a rough (R)form.
The Rbacteria were harmless, but the Sbacteria were
lethal when injected into mice. Heat-killed Scells were
also harmless.
DNA as Genetic Material
http://en.wikipedia.org/wiki/Frederick_Griffithhttp://en.wikipedia.org/wiki/Frederick_Griffith8/12/2019 DNA Technology Lect 1
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Surprisingly when live Rcells were mixed with
killed Scells and injected into mice the mice died,
and the bacteria rescued from the mice had been
"transformed" into the Stype.
This experiment strongly implied that geneticmaterial had been transferred from the dead (S)to
the live cell (R).
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The Discovery o f DNA as the Genetic Material
Hershey and Chasedetermined that viral DNA, not protein shell,
enters cell upon infection to produce more virus particles
The Scientific Method
Observation:A kind of virus called T2 infects the bacterium
Escher ichia col iand essentially turns the bacterium into a T2-factory by inserting viral genetic code into the bacterium.
Question:Since viruses are composed of DNA (some have RNA
instead) in a protein coat/shell called a capsid, which of these
two is the viral genetic material? Is the viral DNA or the protein
inserted into the E. co lito direct the synthesis of more T2
virus?
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Procedure
Step 1:Hershey and Chase grew two separate batches of T2 virus(bacteriophage) and E. co li:
one with radioactive sulfur and one with radioactive phosphorus
Radioactive
Sulfur
(in protein)
Radioactive
Phosphorus
(in DNA)
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Step 2:The radioactive T2 were isolated from each of the
containers and placed into separate, new batches of E. co li.
Step 3:Separately, each mixture was spun in a centrifuge to
separate the heavy bacteria (with any viral parts that had
gone into them) from the liquid solution they were in
(including any viral parts that had not entered the bacteria).
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Radioactive
Sulfur
(in protein)
Radioactive
Phosphorus
(in DNA)
Supernatant
Pellet
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Result
In the batch of T2 that had been grown with radioactive
phosphorus, radioactivity was found in the bacterial
pellet but not the supernatant, indicating that the viral
DNA did go into the bacteria.
In the batch of T2 that had been grown with radioactive
sulfur, radioactivity was found in the supernatant but notthe pellet, indicating that the viral protein did not go into
the bacteria.
Conclusion
It was concluded that the viral DNA is
the genetic code material
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Role of DNA
It is now well established that, thebank of genetic
information takes the form of a stable macromolecule, DNA.
DNA serves as the carrier of genetic informationin both
prokaryotes and eukaryotes .
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It is clear that the properties of cells are to a large
extent determined by their constituent proteins.
Many proteins serve as indispensable structural
components of the cell.
Other proteins, such as enzymes and certain
hormones, are functional in character and determine
most of the biochemical properties of the cell
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As a result, the factor that controls the type and
quantity of which protein a cell may synthesize is
the same factor that determines the function ofevery living cell.
DNA is relatively inert chemically. The information it
contains is expressed indirectly via other molecules.
DNA directs the synthesis of specific RNA and protein
molecules, which in turn determine the cell's chemical
and physical properties.
This role for DNA is called the Central dogmaof
molecular biology.
http://esg-www.mit.edu:8001/esgbio/dogma/repl.htmlhttp://esg-www.mit.edu:8001/esgbio/dogma/repl.htmlhttp://esg-www.mit.edu:8001/esgbio/dogma/repl.htmlhttp://esg-www.mit.edu:8001/esgbio/dogma/repl.html8/12/2019 DNA Technology Lect 1
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It is now well recognized that DNA is the macromolecule
that controls every aspect of cell function.
This is done through protein synthesis as suggested by the
following sequences:
DNA
mRNA Gene product (protein)
Transcription
Translation
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The transfer of information from DNA to protein
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http://en.wikipedia.org/wiki/Nucleic_acidhttp://en.wikipedia.org/wiki/Nucleic_acidhttp://en.wikipedia.org/wiki/Nucleic_acid8/12/2019 DNA Technology Lect 1
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Ribonucleic acidor RNAis a nucleic acid, consisting
of many nucleotidesthat form a polymer.
Each nucleotide consists of a nitrogenous base, aribosesugar, and a phosphate.
RNA is very similar to DNA, but differs in a few
important structural details:
- in the cell RNA is usually single stranded, whileDNA is usually double stranded.
- RNA nucleotides contain ribose while DNA
contains deoxyribose.
-In RNA the nucleotide uracilsubstitutes for
thymine, which is present in DNA.
http://en.wikipedia.org/wiki/Nucleic_acidhttp://en.wikipedia.org/wiki/Nucleotidehttp://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Nucleobasehttp://en.wikipedia.org/wiki/Ribosehttp://en.wikipedia.org/wiki/Phosphatehttp://en.wikipedia.org/wiki/Deoxyribosehttp://en.wikipedia.org/wiki/Uracilhttp://en.wikipedia.org/wiki/Thyminehttp://en.wikipedia.org/wiki/Thyminehttp://en.wikipedia.org/wiki/Uracilhttp://en.wikipedia.org/wiki/Deoxyribosehttp://en.wikipedia.org/wiki/Phosphatehttp://en.wikipedia.org/wiki/Ribosehttp://en.wikipedia.org/wiki/Nucleobasehttp://en.wikipedia.org/wiki/Nucleobasehttp://en.wikipedia.org/wiki/Nucleobasehttp://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Nucleotidehttp://en.wikipedia.org/wiki/Nucleic_acidhttp://en.wikipedia.org/wiki/Nucleic_acidhttp://en.wikipedia.org/wiki/Nucleic_acid8/12/2019 DNA Technology Lect 1
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RNA is transcribed with only four bases (adenine, cytosine,
guanine and uracil).
However, there are numerous modified bases and sugars
in mature RNAs:
1- Pseudouridine(), in which the linkage between uracil
and ribose is changed from a CN bond to a CCbond.
2- Ribothymidine (T), are found in various places (most
notably in the TC loop of tRNA).
3-Hypoxanthine, a deaminated guanine base whose
nucleosideis called inosine. Inosine plays a key role in the
wobble hypothesisof the genetic code.
http://en.wikipedia.org/wiki/Pseudouridinehttp://en.wikipedia.org/wiki/TRNAhttp://en.wikipedia.org/wiki/Nucleosidehttp://en.wikipedia.org/wiki/Inosinehttp://en.wikipedia.org/wiki/Wobble_hypothesishttp://en.wikipedia.org/wiki/Genetic_codehttp://en.wikipedia.org/wiki/Genetic_codehttp://en.wikipedia.org/wiki/Wobble_hypothesishttp://en.wikipedia.org/wiki/Inosinehttp://en.wikipedia.org/wiki/Nucleosidehttp://en.wikipedia.org/wiki/TRNAhttp://en.wikipedia.org/wiki/Pseudouridine8/12/2019 DNA Technology Lect 1
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1- Messenger RNA (mRNA)
Is synthesized from a gene segment of DNA which
ultimately contains the information on the primarysequence of amino acids in a protein to be synthesized.
The genetic code as translated is for m-RNA not DNA.
The messenger RNA carries the codeinto thecytoplasm where protein synthesis occurs.
Types of RNA
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mRNA is heterogeneous in size and sequence. It always
has a 5 ' capcomposed of a 5' to 5' triphosphate linkage
between two modified nucleotides: a 7-methylguanosineand a 2 ' O-methyl purine.
This cap serves to identify this RNA molecule as an mRNA
to the translational machinery.
Most mRNA molecules contain a poly-adenosine tail at the
3' end.
Both the 5' capand the 3' tailare added after the RNA istranscribed and contribute to the stability of the mRNA in the
cell.
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mRNA
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tRNA is the information adapter molecule.
It is the direct interface between amino-acid
sequence of a protein and the information in DNA.
Therefore it decodes the information in DNA.
There are > 20 different tRNA molecules. All have
between 75-95 nt.
All tRNA's from all organisms have a similarstructure, indeed a human tRNA can function in
yeast cells.
2- Transfer RNA (tRNA)
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tRNA
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Ribosomal RNA (rRNA) is a component of theribosomes, the protein synthetic factories in the cell.
Eukaryotic ribosomes contain four different rRNA
molecules: 18 s, 5.8 s, 28 s, and 5 s rRNA(s stands forsedimentation coefficient).
rRNA molecules are extremely abundant. They make
up at least 80% of the RNA molecules found in a typical
eukaryotic cell.
3- Ribosomal RNA (rRNA)
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How is Inform at ion Stored?
One strand of the DNA double-helix (anti-sense strand)
serves as a template for the construction of mRNA.
The sequence of nucleotides in this DNA strand is
complimentary (opposite) the sequence in mRNA.
The sequence of nucleotides in mRNA determines the
amino acids in the protein. For example GUG in mRNA (or
CAC in DNA) codes for valine.
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The strand of DNA that contains the genetic code is
called the anti-sense.
It is often referred to as the coding strand or the
template strand.
The other strand (the sense strand) is not used. Noticethat the sense strand has the same base sequence as
mRNA except that mRNA has U instead of T.
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The codes in DNA are copied to produce mRNA.
Each three-letter code in mRNA (called a codon)
codes for one amino acid.
The sequence of amino acids in proteins is therefore
most directly determined by the sequence of codonsin mRNA, which in turn, are determined by the
sequence of bases in DNA.
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Second Base
U C A G
F
i
r
s
t
B
a
s
e
U
UUU Phe UCU Ser UAU Tyr UGU Cys U
T
h
i
r
d
B
a
s
e
UUC Phe UCC Ser UAC Try UGC Cys C
UUA Leu UCA Ser UAA Stop UGA Stop A
UUG Leu UCG Ser UAG Stop UGG Trp G
C
CUU Leu CCU Pro CAU His CGU Arg U
CUC Leu CCC Pro CAC His CGC Arg C
CUA Leu CCA Pro CAA Gln CGA Arg A
CUG Leu CCG Pro CAG Gln CGG Arg G
A
AUU Ile ACU Thr AAU Asn AGU Ser U
AUC Ile ACC Thr AAC Asn AGC Ser C
AUA Ile ACA Thr AAA Lys AGA Arg A
AUG Met
or StartACG Thr AAG Lys AGG Arg G
G
GUU Val GCU Ala GAU Asp GGU Gly U
GUC Val GCC Ala GAC Asp GGC Gly C
GUA Val GCA Ala GAA Glu GGA Gly A
GUG Val GCG Ala GAG Glu GGG Gly G
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