PreAP Application
of Genetics 2015
Gene Therapy
http://news.discovery.com/human/videos/how-does-genetherapy-work-video.htm
Testing for Alleles
 Genetic
disorders have
slightly different DNA
sequences from their
normal counterparts.
A
variety of genetic tests have been developed
that can spot those differences.
 Enables
prospective parents to see if they are
carriers of a genetic disorder such as Tay-Sachs
or cystic fibrosis.
Genetic Tests
 Genetic
tests are now available
for hundreds of disorders.
 Makes
it possible to determine
whether prospective parents risk
passing such alleles to their children.
 Can
pinpoint the exact genetic basis
of a disorder, and therefore make it
possible to develop more effective
treatment.
Gene Therapy
 Gene
Therapy - Process of
changing the gene that
causes a genetic disorder in
order to eliminate the cause of
the disorder
 An
absent or faulty gene is
replaced by a normal, working
gene.
 Replacing
a mutated gene:
A
gene called p53 normally prevents tumor growth in your body. If
doctors could replace the defective p53 gene, that might trigger the
cancer cells to die.
Fixing a mutated gene:
Mutated genes that cause disease could be turned off so that they
no longer promote disease, or healthy genes that help prevent
disease could be turned on so that they can inhibit the disease.
Making diseased cells more evident to the immune system.
 In some cases, your immune system doesn't attack diseased cells
because it doesn't recognize them as intruders. Doctors could use
gene therapy to train your immune system to recognize the cells that
are a threat.

History of Gene Therapy

1990 - First authorized attempt to
cure a human genetic disorder
by gene transfer.

1999 - A young French girl was
cured of an inherited immune
disorder when cells from her
bone marrow were removed,
modified in the laboratory, and
then placed back in her body.
The patient above is 18 yrs. old and has
been receiving monthly blood transfusions
since the age of 3 because of a genetic
disorder he has. An international team of
scientists have managed to partially
correct his genetic faults, granting him his
independence from the blood transfusions.
He hasn’t needed a transfusion at all during
the last 21 months!
Gene Therapy:
Using Viruses

Viruses are often used because of
their ability to enter a cell's DNA.
1.
The virus particles are modified so that
they cannot cause disease.
2.
Then, a DNA fragment containing a
replacement gene is spliced to viral DNA.
3.
The patient is then infected with the modified
virus particles, which should carry the gene
into cells to correct genetic defects.
Other Genetic Testing Methods: DNA
Fingerprinting

DNA Fingerprinting - Analysis of sections of DNA that
have little or no known function, but vary widely
from one individual to another, in order to identify
individuals.

Does not analyze the cell's most important genes
because they are largely identical among most
people.

Samples can be obtained from blood, sperm, and
even hair strands with tissue at the base.

Used in Forensic Science: Has helped convict
criminals as well as overturn many convictions

Used to determine paternity
Gene Therapy- A Promising Cure?

Unfortunately, gene therapy experiments have not
always been successful.
 Attempts
to treat cystic fibrosis by spraying genetically
engineered viruses into the breathing passages have not
produced a lasting cure.

For all the promise it holds, in most cases gene
therapy remains a high-risk, experimental procedure.
Genetic Engineering
Genetic Variation

You can compare dogs of every breed
imaginable!

There is an enormous range of
characteristics that are the result of
genetic variation.

The differences among breeds of dogs
are so great that someone might think
that many of these breeds are different
species.

They're not, of course, but where did
such differences come from?
Selective Breeding

The answer, of course, is that we did it.
 Humans
have kept and bred dogs for thousands of
years, always looking to produce animals that might
be better hunters, better retrievers, or better
companions.

By selective breeding, allowing only those
animals with desired characteristics to produce
the next generation, humans have produced
many different breeds of dogs.
Selective Breeding

Humans use selective breeding, which takes
advantage of naturally occurring genetic
variation in plants, animals, and other organisms,
to pass desired traits on to the next generation of
organisms.
 Nearly
all domestic animals—including horses,
cats, and farm animals—and most crop plants
have been produced by selective breeding.
Selective Breeding

The ancestor of modern corn
had tiny kernels, each
protected by a tough husk.

Domestication of maize, which
began thousands of years ago,
selected for large sheathed
cobs containing large kernels
without husks.
Hybridization
 Hybridization
- Breeding technique that
involves crossing dissimilar individuals to bring
together the best traits of both organisms.
 Hybrids,
the individuals produced by such
crosses, are often hardier than either of the
parents.
Zeedonk - Zebra and Donkey
Liger – Lion and Tiger
Jaglion- Jaguar and Lion
Inbreeding

To maintain the desired characteristics
of a line of organisms, breeders often use a
technique known as inbreeding.

Inbreeding is the continued breeding of
individuals with similar characteristics.

The many breeds of dogs—from beagles to
poodles—are maintained by inbreeding.
Inbreeding helps to ensure that the
characteristics that make each breed
unique will be preserved.
Risks of Inbreeding

Although inbreeding is useful in retaining a certain set of
characteristics, it does have its risks.
 Most
of the members of a breed are genetically similar.
 Because
of this, there is always a chance that a cross between
two individuals will bring together two recessive alleles for a
genetic defect.
 Serious
problems in many breeds of dogs, including blindness
and joint deformities in German shepherds and golden
retrievers, have resulted from excessive inbreeding.
Increasing Variation

Selective breeding would be nearly impossible without
the wide variation that is found in natural populations.

This is one of the reasons biologists are interested in
preserving the diversity of plants and animals in the wild.

However, sometimes breeders want more variation than
exists in nature.

Breeders can increase the genetic variation in a
population by inducing mutations, which are the ultimate
source of genetic variability.
Increasing Variation

As you may recall, mutations are inheritable changes in
DNA.

Mutations occur spontaneously, but breeders can increase
the mutation rate by using radiation and chemicals.

Many mutations are harmful to the organism.

With luck and perseverance, however, breeders can
produce a few mutants—individuals with mutations—with
desirable characteristics that are not found in the original
population.
Producing New Kinds of Plants

Drugs that prevent chromosomal
separation during meiosis have
been particularly useful in plant
breeding.

Sometimes these drugs produce
cells that have double or triple the
normal number of chromosomes.

Plants grown from such cells are
called polyploid because they
have many sets of chromosomes.
Polyploidy: the condition of
having three, four, or more sets
of chromosomes instead of the
two present in diploids.
Polyploidy

Polyploidy is usually fatal in animals.

However, for reasons that are not clear, plants are much
better at tolerating extra sets of chromosomes.

Polyploidy may instantly produce new species of plants
that are often larger and stronger than their diploid
relatives.
Genetic Engineering

Genetic Engineering - Process of making changes in
the DNA code of living organisms.
Recombinant DNA

Recombinant DNA - DNA produced
by combining DNA from different
sources.
 Can
join “synthetic” sequences to
“natural” ones using enzymes that splice
DNA together.
 Is
possible to take a gene from one
organism and attach it to the DNA of
another organism by using enzymes.
Bacteria Transformation

Plasmid - Circular DNA molecule found in
bacteria.
 Plasmids
are found naturally in some bacteria
and are useful for DNA transfer. Why?
1.
It’s DNA sequence promote plasmid
replication.

2.
Ensures the transformed bacteria will
be replicated.
Plasmids contain a genetic marker —a
gene that makes it possible to distinguish
bacteria that carry the plasmid and the
foreign DNA from those that don't.
Bacteria Transformation
Is it Possible to Transfer Whole Genes
From One Organism to Another?

In 1986, American researcher Steven
Howell transferred the gene for
luciferase into tobacco plant cells.
 Luciferase
is an enzyme that allows
fireflies to glow.
 The
plants glowed in the dark!
Transgenic Organisms

Transgenic - Term used to refer to an organism that
contains genes from other organisms.
1.
Transgenic Bacteria
 Reproduce
rapidly and are easy to grow.
 Produce a host of important substances such as insulin,
growth hormone, and clotting factor which are used to
treat serious human diseases and conditions.
 Oil eating bacteria help clean up oil spills
 Bacteria transformed with the genes for human
proteins now produce these important
compounds cheaply and in great abundance.
Transgenic Organisms
2.
Transgenic Animals

Used to study genes and to improve the food supply.
 Mice
have been produced with human genes that make
their immune systems act similarly to those of humans.
 Allows
scientists to study the effects of diseases on the
human immune system.
 Some
transgenic livestock now have extra copies of
growth hormone genes.
 Grow
faster and produce leaner meat
Transgenic Organisms
3.
Transgenic Plants

Are now an important part of our food supply.

In the year 2000, 52% of the soybeans and 25% of the corn grown in
the US were transgenic, or genetically modified (GM).

Some GM plants contain genes that produce a natural insecticide.


The crops do not have to be sprayed with synthetic pesticides.
Other crop plants have genes that enable them to resist weedkilling chemicals.

Allows crops to survive while weeds are still controlled.
Cloning
 Clone
- Member of a population of genetically
identical organisms produced from a single cell.
 Cloned
colonies of bacteria and other
microorganisms are easy to grow, but this is not
always true of multicellular organisms,
especially animals.
Cloning Animals


In 1997, Scottish scientist Ian Wilmut stunned
biologists by announcing that he had cloned
a sheep, which he later named Dolly.
How did he do it?
1.
Take the nucleus of any female’s egg cell
and remove it.
2.
This cell is fused with a somatic body cell
(this is the cell you want to make a clone of)
taken from another adult.
3.
The fused cell is tricked into thinking its
fertilized and begins to divide.
4.
The embryo is then placed in the
reproductive system of a foster surrogate
mother, where it develops normally.
Cloning

Cloned cows, pigs, mice, and other mammals have been
produced by similar techniques.

Researchers hope that cloning will enable them to make copies
of transgenic animals and even help save endangered species.

On the other hand, the technology is controversial for many
reasons, including studies suggesting that cloned animals may
suffer from a number of genetic defects and health problems.

The use of cloning technology on humans, while scientifically
possible, raises serious ethical and moral issues that have
caused many people to oppose such work. As techniques
improve, these important issues will become even more
pressing.
Clone
Member of a CC with surrogate Genetic mom
mom
population of
genetically identical
organisms produced
from a single cell.
CC = Copy Cat (the clone)
CC gives birth
to 3 healthy
kittens
Online Cloning Lab
Due Tuesday, 12/8