Chapter 13 – Recombinant
DNA and Genetic Engineering
College Prep Biology
Mr. Martino
Introduction
• Gene Therapy: transfer of one or more modified
genes into an individual’s cells
– Correct genetic defect
– Boost immune system
• Recombinant DNA Technology: science of
cutting and recombining DNA from different species
– Genes are then placed into bacterial, yeast or mammalian
cells and replicated
• Genetic Engineering: genes are isolated,
modified, and inserted back into a cell
– also called biotechnology
15.1 Making Recombinant DNA
• Restriction enzyme:
enzyme that chops up DNA
at a specific sequence
– Bacterial
– Viral defense mechanism
– May cut a DNA strand a
few times
– Helpful in studying DNA
– Produces “sticky ends”
which may pair with other
DNA
• Genome: all the DNA in a
haploid number of
chromosomes for each
species
• Plasmids: small circle of DNA
– In bacterial cells
– Insert foreign DNA (gene) into and
put back in bacteria – reproduces
naturally making a DNA clone
– Cloning vector: plasmid used to
accept foreign DNA and replicate
it
• Reverse transcriptase: enzyme
from RNA viruses that perform
transcription in reverse (RNA to DNA)
– cDNA: (copied DNA) mature
mRNA transcript that has already
been spliced
• Bacteria cannot remove introns
and splice exons
• Reverse transcriptase makes
DNA from mRNA to insert into
plasmid
15.2 PCR – Polymerase Chain
Reaction
• PCR: a fast method of
amplifying (making lots of
copies) DNA
– DNA isolated, mixed with DNA
polymerase, nucleotides, and
some other good stuff
• Produces 2 daughters
• Daughters replicate, etc.
• 1 DNA molecule generates
100 billion in a few hours
– Used in evolution research,
analyze DNA from fossils,
analyze embryos, court cases
15.3 DNA Fingerprints
• No two people have
exactly identical DNA
– Except identical twins
• DNA Fingerprint:
unique set of DNA
fragments
– Used to determine
paternity, solve crimes, etc.
– 99.9% all human DNA is
identical
– Focus on highly variable
areas of tandem repeats
• Mutations occur within
families and are more
common in these areas
• Gel electrophoresis: uses an
electric current to force DNA
fragments through a gel
– DNA is negative
– Size of fragment determines
how far it migrates
• The fewer tandem
repeats the farther it
travels
• Differences in
homologous DNA
sequences resulting in
fragments of different
lengths are restriction
fragment length
polymorphisms
(RFLP’s)
15.4 DNA Sequencing
• 1995 – entire DNA
sequence for a
bacterium was
determined
• 4/25/03 – Human
genome completed
• Several bacteria, yeast,
Drosophila,C. elegans worm, Arabidopsis weed, Mickey…a mouse,
just completed 3/31/04
– a rat)
• Used a sequencing
machine
15.5 Isolating Genes
• Genomic Library: set of
DNA fragments from an
organism’s genome
• Complementary RNA
sequence can be
synthesized with a
radioactive isotope tag
called a probe
– Used to find a specific
gene
– Tags the gene
whenever encountered
– Gene may then be
isolated
15.6 Using the Technology
• True human insulin is
now manufactured
• Also somatotropin
(growth hormone),
blood-clotting factors,
hemoglobin,
interferons (cancer
research), and various
other drugs and
vaccines
• Bacteria for oil spill
clean up and other
environmental
pollution
15.7 Designer Plants
• Genetically engineered
plants have been
developed for
pharmaceuticals,
herbicide, pest, and
disease resistance, larger
and tastier plants, fruits,
and vegetables with
greater yields
– Corn, cotton, potato, soy bean,
etc
15.8 Gene Transfers in Animals
• Cloning holds
promises for future
– Clone organs and
tissues
– Possibly modify
animals to be more
disease resistant
and produce
greater quantities
of products
– Not currently
occurring in farm
animals
• 1997 – the first animal was
cloned – Dolly a lamb
– 1. Remove nucleus from
cell
– 2. Transfer nuclei from
desired cells into
unfertilized eggs
– 3. Implant the “zygote”
into surrogate mother
– Since Dolly – we have
cloned mice, rats, cows,
cats, mules, horses, and
Rhesus monkeys along
with a couple of
endangered animals
Human Genome
• HGP – an int’l effort to map and
sequence all human genes
– 15 countries started 11/1/90 and
finished 4/25/03 (50 years after
Watson & Crick paper published)
– 1. Genome – only 30,000
genes so it took less time
• Includes mapping &
sequencing of other
species for comparison
– 2. RNA transcription – more
difficult since 30,000 genes
code for 80,000 proteins due
to alternative splicing
– 3. Proteome – quest for every
human protein
15.9 Who Gets Enhanced?
• HGP already has an ethics committee due to
insistence of James Watson
– HGP needs to be used to help people and must
be regulated by laws
– Must prevent invasion of privacy and
discrimination by insurance companies,
employers,etc.
– Must prevent Eugenics: purging of
“undesirable” traits from human population
(Hitler)
– Science provides society with knowledge and
opportunities – society requires rules and
constraints to prevent abuse