Molecular Biology
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DNA Fingerprint – a sequence of bands that shows a
persons DNA sequence
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How to make a DNA Fingerprint
1. DNA Extraction
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Cell is opened and the DNA is separated from the
other cell parts
2. Cutting DNA
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DNA is so long we cut it into smaller fragments
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Restriction Enzymes – cut DNA at a specific sequence
of nucleotides
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EcoRI - CTTAA
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Bam I - CCTAG
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Ex: ACTGCTTAAGGCATTGCCTTAACAGGCTA
Ex: GCTTACCCTAGATGACGTTACTTACAGGC
Hae III - CCGG
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Ex: CCGATACGCTCCGGACTACCGGATCCGGAT
3. Separating DNA
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Gel Electrophoresis – a technique for separating DNA
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DNA is negatively charged
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Load DNA into gel
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Apply electric voltage to gel
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DNA will move through gel to positive
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Smaller DNA fragments move faster and further
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How do you end up with different size fragments that are
unique to each individual?
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Tandem Repeat – region of a chromosome that
contains multiple copies of a DNA sequence
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The origin and significance of tandem repeats is a
mystery
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For forensic scientists they offer a means of
distinguishing one individual from another through DNA
fingerprinting
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30% of human genome is composed of tandem repeats.
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Tandem repeats seem to act as filler or spacers
between the gene regions of DNA
1
2
3
FROM
BLOOD
AT CRIME
SCENE
4
5
6
7
Fig. 16.7, p. 259
PCR
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PCR – Polymerase Chain Reaction – process of making
many copies of genes
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Heat DNA to separate two strands
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As it cools DNA polymerase starts making copies
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Repeat this process and end up with millions of copies
Polymerase Chain Reaction (PCR)
DNA heated to
separate strands
DNA polymerase adds
complementary strand
DNA fragment to be
copied
PCR cycles
1
2
3
4
5 etc.
DNA copies
1
2
4
8
16 etc.
13-3 Cell Transformation
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Transformation – one organism is changed by a gene or
genes from another organism
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Genetic Engineering – method of cutting DNA from one
organism and inserting the DNA into another organism
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Recombinant DNA – DNA made by recombining fragments
of DNA from different sources
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Plasmid
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Extra circular DNA found in some bacteria
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Very useful for DNA transfer from one organism into
another
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Process of Transformation
1. Cut out gene of interest with restriction enzyme
2. Use same restriction enzyme to cut plasmid
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This creates ends on each that will match up
3. Combine the gene of interest with the plasmid
4. Place the recombinant DNA into a bacteria cell
5. Bacteria will replicate this new DNA and make many
copies of the gene of interest
13-4 Applications of Genetic Engineering
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When recombinant DNA is put into a host that organism
will use the foreign DNA as if it were its own.
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Transgenic Organisms – contain functional foreign DNA
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Ex. Glowing bacteria
Fig. 16.12, p. 263
Application of DNA Technology
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Transgenic bacteria in agriculture
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A bacteria on strawberry plants promotes frost damage
on leaves. The gene for this protein is removed and
frost damage is prevented.
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A bacteria that lives in soil and in the roots of plants
can be engineered to increase the rate of conversion of
atmospheric nitrogen to nitrates, a natural fertilizer, to
help cut back on fertilizer use and cost
Transgenic bacteria in industry
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Used to clean up oil spills
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Extract valuable minerals from ores
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Transgenic bacteria in medicine
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The production of growth hormone to treat dwarfism
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Human insulin used to treat diabetes
Transgenic plants
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Have been genetically engineered to resist herbicides,
produce internal pesticides or increase their protein
production.
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Produce rice with vitamin A
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In 2000 52% of soybeans and 25% of corn grown in US
was genetically modified
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Transgenic Animals
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Make animals grow faster and produce leaner meat
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Trying to produce chickens resistant to bacterial
infections that cause food poisoning
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Cows produce different human proteins in their milk
Cloning
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Clone – genetically identical offspring produced from a
single cell
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In 1997 Scottish scientist Ian Wilmut cloned first mammal,
a sheep named Dolly
14-3 Human Molecular Genetics
Human Genome Project
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Human Genome Project
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An international effort to completely map and sequence
the human genome
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Started in 1990 and completed in 2000
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How did they do it?
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First determined markers – a sequence of bases in
widely separated regions of DNA
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Cut DNA into random fragments
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Determined sequences of the fragments
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Computers found areas of overlap between the
fragments
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One surprise was how few genes humans have
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Fruit fly – 14,000
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Tiny worm – 20,000
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Human – 25,000
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A human diploid cell contains more than 3 billion base
pairs
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Only about 2% of the DNA in your chromosomes functions
as genes
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The average human gene consists of about 3000 base
pairs
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The largest gene in the human genome has more than 2
million base pairs
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Chromosome 22 and 21 were the first 2 human
chromosomes sequenced
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Chromosome 22
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Contains approximately 43 million base pairs
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545 genes
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1 causes leukemia
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1 neurofibromatosis
Chromosome 21
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Approximately 32 million base pairs
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225 genes
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Lou Gehrigs disease (ALS) – loss of muscle control due
to destruction of nerves in the brain and spinal cord