Title: nucleic acid
1NUCLEIC ACID
2NUCLEIC ACID
- Nucleic acids are biological macromolecules
- They are members of a family of biopolymers
essential for life, and include DNA and RNA - nucleic acids function in encoding, transmitting
and expressing genetic information. - Nucleic acids were first discovered by Friedrich
Miescher in 1871.
3Molecular composition
- Each nucleotide consists of three components a
purine or pyrimidine nucleobase, a pentose sugar,
and a phosphate group. - The sugars and phosphates are connected to
phosphodiester linkages
4DNA RNA
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7Pirimidine and Purine bases
- Pyrimidine and Purine are heterocyclic aromatic
organic compound - Pirimidine basesCytosin,Urasil and Thymine
- Purine basesAdinine and guanine
8Adininine
- Adenine (a purine derivative) 9H-purin-6-amine
- A chemical component of DNA and RNA.
- The shape of adenine is complementary to either
thymine in DNA or uracil in RNA.
9Guanine
- Guanine (a purine derivative)
- found in DNA and RNA
- guanine is only paired with cytosine.
- 2-amino-6-hydroxypurine
10Cytosine
- Cytosine found in DNA and RNA
- It is a pyrimidine derivative
- It forms three hydrogen bonds with guanine
- 4-amino-1H-pyrimidine-2-one
11Thymine
- Thymine (pyrimidine nucleobase) found only in DNA
- Thymine is also known as
5-Methylpyrimidine-2,4(1H,3H)-dione
(5-methyluracil) - Thymine (T) binds to adinine (A) via two hydrogen
bonds
12Uracil
- Uracil (pyrimidine derivative) found only in RNA.
- uracil (U) binds to adenine (A) via two hydrogen
bonds. - 2,4-dihydroxypyrimidine
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14Phosphodiester bond
- A phosphodiester bond is a group of strong
covalent bonds between a phosphate group and two
5-carbon ring carbohydrates (pentoses) over two
ester bonds.
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18Chargaffs Rules
- Erwin Chargaff (1947) provides more evidence that
DNA genetic material - Analysis of base composition of DNA compared
between different organisms - Nitrogenous bases
- Adenine (A)
- Thymine (T)
- Guanine (G)
- Cytosine (C)
- Conclusions of Chargaff
- DNA composition is species specific
- The amounts of A,G,C and T are not the same
between species - Ratios of nitrogenous bases vary between species
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20Deoxyribonucleic acid
- DNA contains the genetic instructions used in the
development and functioning of all known living
organisms. - The main role of DNA molecules is the long-term
storage of information - DNA is often compared to a set of blueprints,
since it contains the instructions needed to
construct other components of cells, such as
proteins and RNA molecules. - The DNA segments that carry this genetic
information are called genes
21Structure of DNA
- DNA consists of two long polymer of simple units
called nucleotides, with backbones made of sugars
and phosphate groups joined by ester bonds. - These two strands run in opposite directions to
each other and are therefore anti-parallel. - Attached to each sugar is one of four types of
molecules called nucleobases - It is the sequence of these four nucleobases
along the backbone that encodes information.
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25DNA Double Helix
- The easiest way to visualize DNA is as an
immensely long rope ladder, twisted into a
cork-screw shape. - The sides of the ladder are alternating
sequences of deoxyribose and phosphate (backbone)
while the rungs of the ladder (bases) are made in
two parts with each part firmly attached to the
side of the ladder. - Although most DNA exists as open ended double
helices, some bacterial DNA has been found as a
cyclic helix.
26Properties
- DNA is a long polymer made from repeating units
called nucleotides - DNA of all species comprises two helical chains
each coiled round the same axis, and each with a
pitch of 34 Å and a radius of 10 Å - DNA does not usually exist as a single molecule,
but instead as a pair of molecules that are held
tightly together - The DNA double helix is stabilized primarily by
two forces hydrogen bonds between nucleotides
and base-stacking interactions among the aromatic
nucleobases
27Grooves
- Grooves are spaces between the strands
- These voids are adjacent to the base pairs and
may provide a binding site - The major groove, is 22 Å wide and the minor
groove, is 12 Å wide
Major and minor grooves of DNA
28Alternate DNA structures
- DNA exists in many possible conformations that
include A-DNA, B-DNA, and Z-DNA forms
A, B and Z DNA
29Form Direction Bases/360o Turn HelixDiameter
A Right 11.0 23A
B Right 10.0 19A
Z Left 12.0 18A
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31DNA replication
32Transcription
Initiation Elongation Termination
33Translation
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36RNA
37Ribonucleic acid
- RNA is made up of a long chain of components
called nucleotides. - The sequence of nucleotides allows RNA to encode
genetic information. - All cellular organisms use messenger RNA (mRNA)
to carry the genetic information that directs the
synthesis of proteins. - In addition, some viruses use RNA instead of DNA
as their genetic material perhaps a reflection
of the suggested key role of RNA in the
evolutionary history of life on Earth.
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40Synthesis of RNA
- Synthesis of RNA is usually catalyzed by an
enzymeRNA polymeraseusing DNA as a template, a
process known as transcription. - The DNA double helix is unwound by the helicase
activity of the enzyme. - The enzyme then progresses along the template
strand in the 3 to 5 direction, synthesizing a
complementary RNA molecule with elongation
occurring in the 5 to 3 direction. - The DNA sequence also dictates where termination
of RNA synthesis will occur
41Types of RNA
- Messenger RNA (mRNA)
- Transfer RNA (tRNA)
- Ribosomal RNA (rRNA)
42mRNA
- Messenger RNA is a molecule of RNA encoding a
chemical "blueprint" for a protein product. - mRNA is transcribed from a DNA template, and
carries coding information to the sites of
protein synthesis the ribosomes. - In mRNA as in DNA, genetic information is encoded
in the sequence of nucleotides arranged into
codons consisting of three bases each.
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44tRNA
- Transfer RNA is an adaptor molecule composed of
RNA, typically 73 to 93 nucleotides in length,
that is used in biology to bridge the
three-letter genetic code in messenger RNA with
the twenty-letter code of amino acids in
proteins. - One end of the tRNA carries the genetic code in a
three-nucleotide sequence called the anticodon.
The anticodon forms three base pairs with a codon
in mRNA during protein biosynthesis.
45rRNA
- Ribosomal ribonucleic acid is the RNA component
of the ribosome. - Ribosomal RNA provides a mechanism for decoding
mRNA into amino acids and interacts with tRNAs
during translation by providing peptidyl
transferase activity.
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49Mutations
In biology, mutations are changes to the base
pair sequence of genetic material (either DNA or
RNA). Mutations can be caused by copying
errors in the genetic material during cell
division and by exposure to ultraviolet
or ionizing radiation, chemical mutagens, or
viruses, or can occur deliberately under cellular
control during processes such as meiosis or
hypermutation
50The genetic material (DNA) of a cell can become
damaged or changed. This damage produces
mutations (DNA changes) that affect normal cell
growth and division. When this happens, cells do
not die when they should and new cells form when
the body does not need them. The extra cells may
form a mass of tissue called a tumor.
51Genetic engineering
- Genetic engineering is a scientific development
that involves the artificial manipulation of an
organism's genes by using techniques such as
molecular cloning and transformation in order to
alter their nature and structure. - Many of these transformations are achieved by
manipulation of an organism's DNA, which
effectively is the code inscribed in every cell
to determine how it will function.
52K.Shanmugha Rajan