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Welcome
A key factor in creating genetically modified organisms is
understanding the principles associated with how genetic
information is transferred. We’ve all heard these terms, but how
do they relate to biotechnology?
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Objectives
By the end of today’s lesson, you will be able to…
• Identify the components involved in the creation of the
genetic code
• Differentiate between the two main nucleic acids
• Determine the role transcription and translation play in
protein synthesis
• Recognize the importance of genetic transfer to biotechnology
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DNA/Protein Complex
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Deoxyribonucleic Acid (DNA)
• DNA is a nucleic acid
composed of units called
nucleotides
• Each nucleotide is made up of
a sugar, a phosphate, and a
nitrogen molecule
• The nitrogen molecules, called
bases, are:
–
–
–
–
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Adenine (A)
Guanine (G)
Cytosine (C)
Thymine (T)
DNA’s Structure
The structure of DNA is a called a double helix, which resembles
a twisted, ladder like structure.
Base pairs form the
rung of the ladder
Backbone
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Genetic Code
The sequence of the nucleotides controls the characteristics of
traits or how they are expressed in the organisms. This
sequence, that controls a given trait, is known as a gene.
Gene
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Three Minute Checkup
1. On a sheet of paper draw a DNA nucleotide and correctly
label each part
2. Next, in the image below, complete the DNA sequence on
the other side of the DNA strand
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Ribonucleic Acid (RNA)
RNA is another type of nucleic acid and is central to protein
synthesis, or the process by which cells build proteins.
What differences do you
notice between DNA and
RNA?
1. RNA is single-strained
2. RNA contains uracil
instead of thymine
3. RNA has a different sugar,
ribose
4. RNA has three different
types, or classes
DNA
strand
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Transcription and Translation
Protein synthesis involves both DNA and
RNA. Protein synthesis is a two step process.
Transcription
The process of coping segments of DNA to
complementary segments of RNA.
Translation
The process of taking the complementary
RNA segments from transcription to decode
and sequence to produce specific
polypeptides, or proteins.
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Classes of RNA
• Ribosomal RNA, or rRNA, is the largest of the three classes of
RNA. It plays a key role in the synthesis of proteins by
decoding messenger RNA and interacting with transfer RNA
during translation.
• Messenger RNA, or mRNA, carries the information that is
necessary to sequence amino acids in a protein to the
ribosome where translation will occur.
• Transfer RNA, or tRNA, is the smallest of the RNA classes. Its
role is to bring, or carry, the amino acid to the ribosome
during protein synthesis.
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Transcription Overview
Nucleus
Plant Cell
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Initiation
During initiation, an enzyme called RNA polymerase unzips the
DNA strand and attaches to a promoter.
DNA template
T AT A
Inactive
template
RNA Polymerase
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Elongation
Next, RNA polymerase travels the DNA template strand and uses
complementary base pairings of the DNA template to create an
RNA copy.
DNA template
mRNA
RNA Polymerase
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Termination
Nucleus
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Translation Overview
Amino Acid
Nucleus
mRNA
mRNA
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Plant Cell
Codons
Genes are organized according to the genetic code. The genetic
code functions through a sequence of amino acids, which occurs
in groups of three. The groups of three are called a codon.
Codon
mRNA
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Three Minute Checkup
1. On an index card (or a sheet of paper) write down the steps
in transcription
2. Describe each transcription step in five words or less
3. Using the genetic code card, write the amino acid for each
codon below
1.
2.
3.
4.
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AUG
UCG
GCU
UGA
Initiation
Translation initiation begins by using a start codon. In prokaryotes,
the initiation codon of mRNA is AUG, which is a modified amino
acid, fromylmethionine.
Start
Codon
mRNA
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tRNA Roles
tRNA contains three complementary nucleotides called
anticodons. Once tRNA finds the start codon, a large piece of
ribosome containing a “P” and an “A” site are attached to mRNA.
Anticodon
mRNA
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Elongation
“P” Site
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“A” Site
Termination
Termination is initiated by one of three stop codons (UAA, UAG,
or UGA). At this point, the ribosome splits and the completed
protein is released.
Stop
Codon
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What Does This Mean to Biotechnology?
Gene cassettes are built to regulate when a new gene is
activated or deactivated in a genetically modified plant.
Promoter
The promoter
causes RNA
polymerase to
begin reading the
DNA sequence.
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Gene
Terminator
The terminator
sends a signal
to stop the
transcription
process.
What Does This Mean to Biotechnology?
Plasmid Vector
Recombinant DNA
Bacterium
Donor gene
Plasmid
Transcription
Isolated gene
from the plant
Translation
Donor gene
Protein
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Questions
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