Download Recombinant DNA

Chapter 15:
Genetic
Engineering
Section 15-2:
Recombinant DNA
Copying DNA
 Breeders
relied on natural variation
produced by unpredictable mutations
 Genetic engineers today can transfer
genes from one organism to another,
creating new living things
 Need to isolate DNA, cut it with REs,
separate it with gel electrophoresis
Finding Genes
 If
a scientists is looking for a particular
gene, they can use a technique called
Southern blotting analysis
 Example:
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In 1987 Douglas Prasher was looking for the
gene in jellyfish that creates GFP, green
fluorescent protein
Wanted to isolate and use this gene as a
marker
Finding Genes




Figured out the most likely mRNA sequence
for part of the amino acid sequence
Compared to thousands of others until he
found the exact sequence in the jellyfish
Found the actual gene by taking a gel with
jellyfish DNA that had been cut with REs
Found fragment that bound exactly to
mRNA – this was the gene
Polymerase Chain Reaction
 Technique
used to make multiple copies
of a gene once it is found
 DNA heated to separate strands
 Cooled, primers added
 DNA polymerase produces
complementary strands
 Repeated over and over
Changing DNA
 Scientists
can create custom DNA
molecules and insert them into living cells
 Machines called DNA synthesizers
produce short segments of DNA which
can then be joined to natural sequences
using DNA ligase or other enzyme for
splicing
Combining DNA Fragments
 If
two DNA sequences from two different
organisms are cut with the same RE, their
sticky ends can be matched and they
can be permanently bonded
 Resulting molecules called recombinant
DNA (recombinant DNA technology)
Plasmids and Genetic Markers
 Sometimes
genes were “lost” once they
were inserted because they did not
replicate along with the cell’s regular DNA
 Now add the genes plus a replication
“start” signal
 Technique often used to create
recombinant plasmids in bacteria (extra,
circular DNA), yeasts
 Use markers to identify inserted genes
Transgenic Organisms
 Organisms
that contain genes from other
species
 Produced by inserting recombinant DNA
into genome of host organism
 Contain genetic markers
Transgenic Plants
 Plant
cells often transformed with
Argobacterium, which in nature inserts a
gene into plants that produces tumors
 Scientists deactivate the tumor gene,
replace it with recombinant DNA, which
then transforms plant cells
Transgenic Plants
 Can
also be produced by removing cell
wall and allowing plant cell to pick up
extra DNA, or inject DNA directly
Transgenic Animals
 If
the egg cell is large enough, DNA can
be injected directly into nucleus and
hopefully inserted into chromosomes
 Now we can also eliminate genes by
inserting new recombinant DNA within
them
Cloning
A
clone is a member of a genetically
identical cells produced from a single cell
 Uses a single cell from an adult organism
to grow an entirely new organism –
genetically identical
 Animal cloning involves nuclear
transplantation
Animal Cloning
 Nucleus
of unfertilized egg removed
 Egg cell fused with donor nucleus taken
from adult
 Resulting diploid cell develops into
embryo
 Embryo implanted into uterine wall of
foster mother
 Develops until birth