DNA, RNA, &
Protein Synthesis
Mrs. Morgan
Biology
Discovering DNA
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1928 – F. Griffith discovers that a factor in heat-killed, disease-causing
bacteria can “transform” harmless bacteria into ones that can cause
disease. (pg 287)
1944 – O. Avery and his team determine that genes are composed of DNA.
(pg 289)
1950 – E. Chargaff observed that in any sample of DNA the number of
adenine molecules was equal to the number of thymine molecules. The
same was true for the number of cytosine and guanine molecules.
1951 – L. Pauling & R. Corey determine that the structure of a class of
protein is a helix.
1952 – R. Franklin studies the DNA molecule using a technique called Xray diffraction. (pg 292)
1953 – J. Watson & F. Crick develop the double-helix model of the structure
of DNA. (pg 293)
Source: Biology, Prentice-Hall, Miller-Levine, pg. 292-293
Part I
DNA
DNA
 “DNA is
the nucleic acid that
stores and transmits the genetic
information from one generation
of an organism to the next.”
 Basically, “DNA carries the
genetic code.”
Source: Biology, Miller-Levine, Prentice Hall, page 139
Components & Structure of DNA
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DNA (DeoxyriboNucleic
Acid) is a polymer made
up of units called
nucleotides.
Nucleotides are made up
of three basic parts: 5carbon sugar
(deoxyribose), a
phosphate group, and a
nitrogenous base.
Nucleotides
Source: www.msu.edu.
Nitrogenous Bases
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There are four kinds of
nitrogenous bases in
DNA.
Adenine & Guanine
belong to the group of
compounds known as
purines.
Cytosine & Thymine
belong to the group
pyrimidines.
Source: home.comcast.net
Nitrogenous Bases
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Adenine will ALWAYS pair with Thymine in
DNA
Thymine will ALWAYS pair with Adenine in
DNA
Cytosine will ALWAYS pair with Guanine
Guanine will ALWAYS pair with Cytosine
HYDROGEN BONDS hold the bases
together
Nucleotide Chain
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Individual nucleotides are
joined together to form a
long chain. Note that the
sugars and phosphate
groups form the
backbone of the chain,
and the nitrogenous
bases stick out from the
chain.
Source: www.nicksnowden.net
Double Helix
Double Helix in Review
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
What are the 3 parts of a nucleotide?
Name the 4 nitrogenous bases.
What is the name of the sugar in DNA?
What base pairs with adenine?
What base pairs with cytosine?
What is the structure of DNA called?
What holds the base pairs together?
What makes up the “backbone” of the DNA structure?
How do they know that adenine always pairs with thymine?
What does the shape of DNA look like?
DNA Replication
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“Before a cell divides, it duplicates its DNA in a
copying process called replication. This
process ensures that each resulting cell will
have a complete set of DNA molecules. During
DNA replication, the DNA molecule separates
into 2 strands following the rules of base pairing.
Each strand of the double helix of DNA serves
as a template or model for the new strand.”
Source: Biology, Miller-Levine, Prentice Hall, page 299
Source: science.howstuffworks.com
Source: http://3.bp.blogspot.com
DNA Replication
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Helicase – enzyme that is
capable of unwinding
DNA double helix.
Causes DNA to “unzip”
which is when the
hydrogen bonds are
broken.
DNA Polymerase – joins
individual nucleotides to
produce a DNA molecule.
Primase – synthesize
short RNA sequences.
Source: personal.psu.edu
DNA Replication Review
1.
2.
3.
What causes the strand of DNA to
“unzip”?
What is the goal of DNA replication?
What is holding the strand of DNA
together that eventually breaks?
Part II
RNA
RNA
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RNA (RiboNucleic Acid)
The structure of RNA is similar to DNA, it
consists of a long chain of nucleotides.
RNA is the nucleic acid that acts as a
messenger between DNA and the ribosomes
and carries out the process in which proteins
are made from amino acids.
There are 3 main differences between RNA &
DNA.
DNA
RNA
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Sugar is deoxyribose
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Sugar is ribose
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Thymine
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Uracil (replaces
thymine)
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Double stranded
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Single stranded
Source:http://images
1.clinicaltools.com
Types of RNA
There are 3 main types of RNA that are
involved in the synthesis of proteins. The
assembly of amino acids into proteins is
controlled by RNA.
 Messenger RNA (mRNA)
 Ribosomal RNA (rRNA)
 Transfer RNA (tRNA)
Transcription: RNA synthesis
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Transcription is the process of transferring
information from DNA to RNA.
Due to the fact that DNA is found in the nucleus
and never leaves the nucleus and ribosomes
are found in the cytoplasm,a messenger must
bring the genetic information from the DNA in
the nucleus out to the ribosomes in the
cytoplasm.
Messenger RNA (mRNA) performs this function.
RNA Review
1.
2.
3.
4.
5.
Name the 3 differences between DNA and
RNA.
Name the 3 types of RNA
What is the goal of transcription?
What type of RNA is responsible for
transcription?
Why is transcription necessary?
Part III
Protein Synthesis
Protein Synthesis
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The information that DNA transfers to mRNA is in the form of a
code. This code is determined by the way in which the four
nitrogenous bases are arranged in DNA.
The nitrogenous bases in DNA contain info that directs protein
synthesis. Proteins play an important role in biological systems.
Proteins control biochemical pathways within the cell, they direct
the synthesis of lipids, carbohydrates, and nucleotides, and they
are also responsible for cell structure and cell movement.
Like a manager of a factory, DNA does not work on the assembly
line but it can control what the cell factory makes by issuing orders
to the organelles (workers). Together, DNA and its assistant, RNA,
are directly responsible for making proteins. DNA & RNA are like
nucleic acid executives who run the entire cell factory. Source: Biology, MillerLevine, Prentice Hall, page 148
Protein Synthesis
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Each combination of 3 nucleotides on
messenger RNA is called a codon (a 3
letter code word).
Each codon specifies a particular amino
acid that is to be placed in the polypeptide
chain (protein chain).
Protein Synthesis
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How does messenger RNA actually produce a protein chain? The
decoding of a messenger RNA message into a protein chain is known as
TRANSLATION. The message is being translated from the language of
nulceic acids into a protein chain. The messenger RNA does not produce
a protein chain itself, instead it uses transfer RNA, ribosomal RNA, and
ribosomes.
During translation, messenger RNA binds to the ribosomes on which
ribosomal RNA (rRNA) is found. Amino acids in the cytoplasm are picked
up by transfer RNA (tRNA) and are carried to messenger RNA (mRNA).
The anticodons in transfer RNA attach to the proper codons in messenger
RNA. Thus messenger RNA acts as the pattern for protein synthesis. In
this way, amino acids are brought together in the correct sequence to form
a protein molecule.
Source: Biology, Miller-Levine, Prentice Hall, pg 150, 155
Amino Acid Chart
Source: http://biosphemera.com
Amino Acid Chart
Source: www2.visalia.k12.ca.us
Source: stemcells.nih.gov
Mutations
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Original –
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Deletion
Duplication
Inversion
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–
–
–
ABC*DEF
A C * D E F (loss of all or part of chromosome)
A B B C * D E F (produce extra copies)
A E D * C B F (reverse the direction of parts of
a chromosomes)
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Translocation –
-
ABC*JKL
G H * I D E F (part of one chromosome
breaks off & attaches to another)