Download Genetic Engineering

Genetic Frontiers
Chapter 15
LEARNING OBJECTIVE 1
•
Define genetic engineering
•
Outline the primary techniques used in
recombinant DNA technology,
including genetic probes and DNA
cloning
KEY TERMS
•
GENETIC ENGINEERING
•
•
Manipulation of genes, often through
recombinant DNA technology
RECOMBINANT DNA TECHNOLOGY
•
Techniques used to make DNA molecules by
combining genes from different organisms
Genetic Engineering
Recombinant DNA Technology 1
•
DNA molecules are cleaved at specific
base sequences
•
•
to break them into smaller fragments
Segments of DNA from different sources
are joined, forming recombinant DNA
molecule
•
these molecules are taken into a host cell
Recombinant DNA Technology 2
•
Cells that take up the gene are identified
with a genetic probe
•
The gene may be transcribed and
translated within the host cell
•
leading to production of a protein not
previously produced by the host organism
KEY TERMS
•
GENETIC PROBE
•
A single-stranded nucleic acid used to identify
a complementary sequence by base pairing
with it
Genetic Probe
Bacterial
colonies
Filter paper
1
Radioactively
labeled
nucleic acid
probe is
added
2
1 Bacterial cells are spread on solid
nutrient medium so that only one cell
is found in each location. Each cell
multiplies to give rise to genetically
identical descendants that form a
colony on the medium. A few cells
from each colony are transferred to
special filters.
Filter with
bacteria from
colonies; cells
2 Radioactively labeled probe nucleic
are broken to
acid is added to the filter; the probe
expose the DNA
nucleic acid is single stranded and
contains a sequence of nucleotides
complementary to the gene of interest.
3 Some radioactive 3 Some of the probe nucleic acid forms
nucleic acid probe base pairs with the DNA of some of
the colonies.
molecules form
base pairs with
the DNA of some
colonies
4 Exposed X-ray
film; dark spots
identify colonies
with desired DNA
4 DNA from bacterial cells that contain
the DNA sequence complementary to
the radioactive probe can be detected
by X-ray film.
Fig. 15-6, p. 299
KEY TERMS
•
DNA CLONING
•
Process of selectively amplifying DNA
sequences so their structure and function can
be studied
LEARNING OBJECTIVE 2
•
Explain the actions and importance of
restriction enzymes and ligase
KEY TERMS
•
RESTRICTION ENZYME
•
•
An enzyme used in recombinant DNA
technology to cleave DNA at specific base
sequences
Breaks the DNA molecule into more
manageable fragments
Ligase
•
Segments of DNA from different sources
are joined by the enzyme ligase
Restriction Enzymes
Site of cleavage
A
A
G
C
T
T
T
T
C
G
A
A
Site of cleavage
Sticky end
A
T
A
T
C
G
A
G
C
Sticky end
T
T
A
Fig. 15-2, p. 295
LEARNING OBJECTIVE 3
•
Identify the role of biological vectors,
such as plasmids, in recombinant DNA
technology
•
Describe a biological vector and a
nonbiological method used to
introduce genes into plant cells
KEY TERMS
•
VECTOR
•
•
An agent, such as a plasmid or virus, that
transfers DNA from one organism to another
PLASMID
•
A small, circular DNA molecule that carries
genes separate from the main DNA of a
bacterial cell
Plasmid
Bacterium
Main bacteria DNA
Plasmid
Fig. 15-3, p. 296
A Biological Vector
•
The plasmid of Agrobacterium is an
effective vector for introducing genes into
many plant cells
Constructing Recombinant DNA
Sticky
end
Plasmid from a
bacterium . . .
Sticky
end
DNA from
another
organism
. . . treated with a
Treated
restriction enzyme
with the same
restriction enzyme
A plasmid and
plant DNA are
spliced together
with DNA ligase
Fig. 15-4, p. 297
Sticky
end
Plasmid from a
bacterium . . .
Sticky
end
DNA from
another
organism
. . . treated with a
Treated
restriction enzyme
with the same
restriction enzyme
A plasmid and
plant DNA are
spliced together
with DNA ligase
Stepped Art
Fig. 15-4, p. 297
Identifying Bacteria With
Altered Plasmids
Sites of cleavage
Fragment
1
Fragment Fragment Fragment
2
3
4
Plant DNA
Produce
recombinant
DNA
1
2
2
Gene for
resistance
to antibiotic
Cut with a restriction
enzyme
2
2
3
1 DNA from plant cells is cut into multiple
fragments with a restriction enzyme.
(Only a small part of one chromosome is
shown.)
2 Recombinant plasmids are formed by
cutting plasmids with the same
restriction enzyme, mixing the plasmids
with the segments of plant DNA, and
treating with ligase.
3 Because the recombinant plasmids
retain a gene for resistance to an
antibiotic (R), bacterial cells that contain
the plasmids are resistant to that
antibiotic.
Plate with
antibioticcontaining
medium
4
Bacteria with plasmid
live and multiply
Bacteria without
plasmid fail to grow
4 The bacteria are then grown on an
antibiotic-containing nutrient medium,
and only those that contain the
recombinant plasmid survive.
Fig. 15-5, p. 298
A Nonbiological Method
•
A nonbiological approach to introduce
DNA into plant cells is a genetic “shotgun”
•
Researchers coat microscopic gold or
tungsten fragments with DNA and then
shoot them into plant cells
Genetic Engineering
Plasmid
Foreign gene
Antibiotic-resistant gene
Genetically
engineered
plant cells
Cultured
plant cells
1 Pieces of plant
2
tissue are placed in a
suitable medium,
and the cells grow to
form a clump of
undifferentiated
cells.
Foreign DNA is spliced 3 The plant cells divide
into the crown gall
in tissue culture.
plasmid. The
Each cultured plant
recombinant plasmid is
cell contains the
inserted into
foreign gene.
Agrobacterium
tumefaciens, which
infects plant cells in
culture.
4 Genetically engineered
plants are produced
from the cultured plant
cells through the use of
plant tissue culture
techniques.
Fig. 15-8, p. 301
LEARNING OBJECTIVE 4
•
Define DNA sequencing
KEY TERMS
•
DNA SEQUENCING
•
Procedure by which the sequence of
nucleotides in DNA is determined
DNA Sequencing
•
Automated DNA-sequencing machines
connected to powerful computers let
scientists sequence huge amounts of DNA
quickly and reliably
LEARNING OBJECTIVE 5
•
Define genome
•
Briefly describe the emerging field of
genomics
KEY TERMS
•
GENOME
•
All the genetic material contained in an
individual
KEY TERMS
•
GENOMICS
•
•
Field of biology that studies the genomes of
various organisms
Tries to identify all the genes, determine their
RNA or protein products, and ascertain how
the genes are regulated
LEARNING OBJECTIVE 6
•
Explain how RNA interference is used
to study gene function
KEY TERMS
•
RNA INTERFERENCE (RNAi)
•
Makes use of certain small RNA molecules
that interfere with the expression of genes or
their RNA transcripts
RNA Interference (RNAi)
•
After a protein-coding gene is identified,
the function of that gene is studied using
RNAi to shut the gene off
•
After the gene is silenced, biologists
observe changes in phenotype to
determine function of missing protein
LEARNING OBJECTIVE 7
•
Describe at least one application of
recombinant DNA technology in each
of the following: medicine and
pharmacology, DNA fingerprinting, and
transgenic organisms, specifically
genetically modified crops
Medicine and Pharmacology
•
Escherichia coli have been genetically
engineered to produce human insulin
•
Significant medical benefits to insulindependent diabetics
DNA Fingerprinting
•
Analysis of DNA from an individual
•
Applications
•
•
•
Investigating crime (forensic analysis)
Studying endangered species in conservation
biology
Clarifying disputed parentage
KEY TERMS
•
TRANSGENIC ORGANISM
•
•
A plant or other organism that has foreign
DNA incorporated into its genome
GENETICALLY MODIFIED (GM) CROP
•
A crop plant that has had its genes
intentionally manipulated (transgenic crop
plant)
Genetically Modified (GM) Crops
•
Agricultural geneticists developing GM
plants that are resistant to insect pests,
viral diseases, drought, heat, cold,
herbicides, and salty or acidic soil
GM Crops
LEARNING OBJECTIVE 8
•
Discuss safety issues associated with
recombinant DNA technology
•
Explain how these issues are being
addressed
Safety Issues 1
•
Concerns: Genetically engineered
organisms might be dangerous if they
escaped into the environment
•
Scientists carried out risky experiments in
facilities designed to hold pathogenic
organisms
Safety Issues 2
•
So far, there is no evidence that
researchers have accidentally cloned
hazardous genes or released dangerous
organisms into the environment
•
Scientists have relaxed many of restrictive
guidelines for using recombinant DNA
Safety Issues 3
•
Stringent restrictions still exist where
questions about possible effects on the
environment are unanswered
•
(Example: in research that proposes to
introduce transgenic organisms into the wild)
Animation: Restriction Enzymes
CLICK
TO PLAY
Animation: Formation of
Recombinant DNA
CLICK
TO PLAY
Animation: Use of a Radioactive
Probe
CLICK
TO PLAY
Animation: Transferring Genes Into
Plants
CLICK
TO PLAY