Chapter 15: Genetic Engineering

whooshdisguisingBiotechnology

Dec 14, 2012 (4 years and 10 months ago)

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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:


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