Chapter 15: Genetic Engineering


14 déc. 2012 (il y a 8 années et 10 mois)

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Chapter 15:

Section 15

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


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

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

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

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 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

Produced by inserting recombinant DNA
into genome of host organism

Contain genetic markers

Transgenic Plants

Plant cells often transformed with

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


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

Animal Cloning

Nucleus of unfertilized egg removed

Egg cell fused with donor nucleus taken
from adult

Resulting diploid cell develops into

Embryo implanted into uterine wall of
foster mother

Develops until birth