DNA - Introduction
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Deoxyribonucleic
Acid
Structure:
Replication
Transcription
Translation
DNA
 DNADeoxyribonucleic
Acid
What is this?
•
POLYMER
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A polymer is a large
molecule made up of
smaller molecules
called monomers
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DNA is a polymer
made up of
Nucleotides.
NUCLEOTIDES
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Nucleotides are the
smaller sub-units that
make up a DNA
 Each Nucleotide is
made up of a
 Sugar, Phosphate and
Nitrogen Base
4 NITROGEN BASES
DNA Nitrogen Bases
4 Base Pairs
Held Together by H Bonds
Adenine
(A)
Guanine
(G)
Thymine
(T)
Cytosine
(C)
Complementary
Base Pairs:
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Cytosine always
bonds with guanine
by forming three
hydrogen bonds.
(C-G)
 Adenine always bonds
with thymine by
forming two hydrogen
bonds. (A-T)
DOUBLE HELIX
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The DNA molecule
consists of two
nucleotide chains that
wrap around each
other to form a double
spiral
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Looks like a twisted
ladder
DNA makes you UNIQUE :)
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The order of nucleotides
(NB) will vary in every
organism
 The closer you are in
Evolutionary History- the
closer your DNA will
resemble
 The sequence of
nucleotides forms the
unique genetic information
of an organism
DNA Replication:
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The process of copying DNA
 Takes place during the “S” phase of the cell
cycle…Remember?
Steps of DNA Replication
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DNA will unwind
DNA will “unzip”
down the middle
separating the sides
of the ladder
Steps of DNA Replication
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Free-Floating
nucleotides will come
in and attach to each
existing side of the
original DNA
 This process will
continue until the
entire molecule has
replicated
Outcome of DNA Replication
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Replication will make 2 identical
strands of DNA which can then be
passed on to a new cell during
mitosis or meiosis
 When all the DNA in all the cells
has replicated, there are 2 copies
of the organism’s genetic
information.
DNA
 DNA
is the “Master” copy of an
organisms information code. This
information contains instructions
used to form nearly all enzymes
and proteins.
DNA- Major Functions
 Directing
Protein Synthesis
 Controlling Cell Division
 Inheritance
Why is it called Universal?
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The codons represent
the same amino acids
in all organisms
 Same in humans and
virtually every other
known organism
 Figured out by
studying the DNA of
the bacteria E. Coli
The Other Nucleic Acid- RNA
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RNA stands for Ribonucleic Acids
RNA and DNA are very similar but
they do have three key differences.
Differences between RNA & DNA
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RNA:
Single Sided
Sugar molecule
called RIBOSE
4 Bases- Cytosine,
Guanine, Adenine
and URACIL
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DNA:
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Double sided
Sugar molecule
called
DEOXYRIBOSE
4 Bases-Cytosine,
Guanine, Adenine
and THYMINE
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RNA in involved in
an important
process called
transcription.
The process in
which RNA makes
a copy of DNA
Similar to
Replication.
Transcription!!
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Proteins are
made on
ribosomes in the
cytoplasm of the
cell. Yet DNA is
found only in the
nucleus. How is
information
brought to the
ribosomes for
protein
synthesis?
RNA Transcription .
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DNA must first unwind.
 Enzymes unzip DNA molecule
 Free-floating RNA nucleotides pair
with complementary DNA
nucleotides on one of the DNA
strands
 Guanine pairs with Cytosine
 Adenine pairs with Uracil
RNA Transcription .
 When
the process of base pairing
is completed, the mRNA
molecule breaks away as the
DNA strands rejoin
 The mRNA leaves the nucleus
and enters the cytoplasm to a
ribosome.
RNA Transcription
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(Messenger) mRNA is
the form in which
information moves
from DNA in the
nucleus to the
ribosomes in the
cytoplasm
 Enzymes make a RNA
copy of a DNA strand
The Genetic Code
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DNA holds the instructions to make
proteins.
 Like DNA..Protein is also a polymer
made up of smaller subunits called
Amino Acids
 There are 20 A.A. They combine in
various ways to make various proteins.
The Genetic Code
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You need to look at DNA as being similar to
the alphabet.
 The alphabet has 26 letters which combine to
form 1000’s of words.
 The DNA alphabet only has 4 letters and all
the words are made up of only 3 letters.
 When you “read” DNA you read in group of 3
Nitrogen Bases at a time.
 Groups of 3 are called CODONS
 Each codon will code for a specific Amino
Acid
Translation- Protein Synthesis
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The process of
converting the
information of mRNA
into a sequence of
Amino Acids that will
make a protein
 On your ribosome is
your mRNA with all
the codons and
information from
DNA
Another Form of RNA
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tRNA
Transfer RNA
Single strand
Purpose is to bring the
appropriate amino acid
to the ribosome
Carries the anti-codon
Mutations
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Gene: sequence of DNA nucleotide bases
Gene Mutation: any change in this DNA
sequence of nucleotide bases
Point Mutation: a change in a single base
pair, mistake may or may not interfere with
protein function
Frameshift Mutation: where a single base
pair is added or deleted, this causes a shift in
the reading of the codons by one base
These mutations can occur when the DNA is
replicated, during transcription and
translation