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Chapter 12
Genetic Engineering
12.1
Modifying the Living World
Humans are always trying to improve their
world
What are some desired
traits that breeders
might want to select for
in these food sources?
What would breeders
need to know about each
trait to produce the
desired trait in the
offspring?
Breeding Strategies
By selecting the most productive organism to
produce the next generation people have
found that the productivity of domesticated
species can be increased
Selective Breeding
Selecting a few individuals to serve as parents
for the next generation
The desired characteristic will become more
common
Inbreeding
Used once a “good” organism is produced
Crossing of individuals with similar
characteristics so that those characteristics
will appear in the kids
Organisms are usually closely related
Risks of Inbreeding
Because organisms are genetically similar, the
chances of recessive defects showing up are
higher
Hybridization
Cross between similar individuals
Often involves crossing members of different
but related species
Hybrid vigor – hybrid individual are often
hardier
Example – corn – 10x more
Mutations –
Producing new kinds
of Organisms
Mutation – inheritable changes in the DNA
Can produce organisms with new
characteristics
Breeders can wait for them to appear or cause
them
Mutagen
Substances that cause mutations
Ex. Radiation, chemicals
Works well with bacteria
Bacteria
Very small
Reproduce asexually
Most abundant and diverse organisms in the
world
Some are helpful (bacteria in your intestines,
bacteria that decompose dead organisms)
Some are harmful (food poisoning, colds,
infections)
Structure of Bacteria
No membrane bound organelles
Capsule – surround cell wall – bacteria with
these are more likely to cause disease
Cell wall – maintains the cell’s shape
Pilli – help bacteria stick to surfaces
Flagella – help bacteria move
Chromosome – single DNA molecule – circular –
contains most genes
Plasmid – one molecule of circular DNA
Plasmid
Small circular pieces of DNA found in bacteria
in addition to their chromosomes
Can be removed from bacteria and cut up
using restriction enzymes
A DNA sequence can be inserted into a
plasmid
Plasmids can be easily reinserted back into
the bacteria
12-2 Genetic
Engineering
Last three decades
Powerful new set of techniques that affect
DNA directly
Biologists can engineer a set of genetic
changes directly into an organisms DNA –
Genetic Engineering
Tools for Genetic Engineering
1. Way to cut a gene out of the DNA
2. Combine DNA with DNA of recipient organism
3. Insert combined DNA into new organisms
4. Way to read the sequences in order to
analyze the genes you are manipulating
Restriction Enzymes (Endonucleases)
Proteins that cut genes at specific DNA
sequences
75+ - each recognizes a specific spot
EcoR1 – cuts at the AG site
Bam1 – cuts at the GG site
Hae111 – cuts between C and G
Action of a Restriction
enzyme
DNA Recombination
DNA fragments are incorporated into part of
the recipient cell’s genetic material
Plasmid – small circular DNA molecule in
bacteria
Sticky Ends – single strands of DNA that allow a
gene to be inserted into a plasmid
GGTTATCGCT
TAGCGATCGA
GENE
Recombinant DNA – combined DNA of two
organisms
DNA Insertion
Put recombinant DNA in a mix of bacterial
cells
Some bacteria will pick up the DNA
Clone – large numbers of cells grown from a
single cell
Other ways – injection with a needle
- shot into cells
Foreign DNA into Plasmid
Engineering New Organisms
Transgenic – organisms that contain foreign
genes
Transgenic Bacteria
put genes in bacteria and they make things
humans need
Ex. Growth hormone
Transgenic Plants
Produce natural insecticides
Produce fertilizer
Transgenic Animals
For farming, ranching
Grow faster
Disease resistant
Cloned Animals
“Dolly”
Nucleus of an egg is removed and replaced
with an adult nucleus
Egg is then placed into a foster mom
The newborn is a clone – a genetic copy
12-3 The New
Human
Genetics
Curing genetic diseases – 5% of babies in USA
born with one
Decoding the human genome (determine the
nucleotide sequence of about 3 billion
nucleotides or about100,000 genes and to
map their location on every chromosome)
Completed in June 2000
Personal Id
Diagnosis of disease – 4,000 human genetic
disorders
DNA Fingerprinting
Takes advantage of the fact that large
portions of the human genome are made of
repeat sequences
Repeat sequences have varying lengths
do not code for a protein
A DNA fingerprint – a pattern of bands made
up of specific fragments from an individual’s
DNA
The banding patterns of DNA fragments from
two different individuals may be compared to
establish whether they are related
Can be used to match a criminal to a crime
scene
Making a DNA Fingerprint
RFLP analysis (Restriction Fragment Length
Polymorphism) – method for preparing a DNA
fingerprint
RFLP analysis – involved extracting DNA from a
specimen of blood or other tissue and cutting
it into fragments using restriction enzymes
The number of fragments and the length of
the fragments varies from person to person
Gel Electrophoresis – used to separate the
fragments of DNA
An electric current is passed through a gel and
the fragments sort out by size
The Electric Field
The Fragments Move
Who are the Soldier’s
parents?
Polymerase Chain
Reaction (PCR)
Can be used to quickly make many copies of
selected segments of the available DNA
PCR requires
Fragment of DNA
Supply of the four nucleotides
DNA polymerase (enzyme involved in DNA
replication)
Primers
Primer – an artificially made single-stranded
sequence of DNA required for the initiation of
replication
When all the ingredients are added together
the fragment of DNA is quickly multiplied
Stem Cells
Stem cells can develop into many different
cell types in the body during early life and
growth.
Serve as an internal repair system, dividing
essentially without limit to replenish other
cells
When a stem cell divides, each new cell has
the potential either to remain a stem cell or
become another type of cell with a more
specialized function, such as a muscle cell, a
red blood cell, or a brain cell
Two important characteristics of
stem Cells
Unspecialized cells capable of renewing
themselves through cell division, sometimes
after long periods of inactivity.
Under certain physiologic or experimental
conditions, they can be induced to become
tissue- or organ-specific cells with special
functions
Two Types of Stem Cells
embryonic stem cells
non-embryonic "somatic" or "adult" stem cells.
In the 3- to 5-day-old embryo, called a
blastocyst, the inner cells give rise to the
entire body of the organism, including all of
the many specialized cell types and organs
such as the heart, lung, skin, sperm, eggs and
other tissues.
In some adult tissues, such as bone marrow,
muscle, and brain, populations of adult stem
cells generate replacements for cells that are
lost through normal wear and tear, injury, or
disease.
Given their unique regenerative abilities,
stem cells offer new potentials for treating
diseases such as diabetes, and heart disease.
Much work remains to be done in the
laboratory and the clinic to understand how to
use these cells for cell-based therapies to
treat disease, which is also referred to as
regenerative or reparative medicine.