Genetic Engineering - LBUSD

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Dec 12, 2012 (5 years and 25 days ago)

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Genetic Engineering

Biology

Mrs. Appel

Pgs 247
-
259

Breeding Strategies


Selective Breeding
: Mating individuals
with a desired trait. Ex: milk cows



Inbreeding
: Mating individuals with
similar characteristics. Ex: pure
-
bred
dogs, royal families.


Risks: increased chance of recessive
genetic defects in offspring.

Farmers and ranchers throughout history have tried to
improve plants and animals by selecting the most
desired organisms to breed.

Breeding Strategies


Hybridization
: Mating 2
dissimilar
individuals. Ex: mules


Often involves mating individuals from 2
different species


Hybrid vigor
: offspring are hardier than
parents

Mutations


Mutation
: Change in the DNA code.


Breeders may use
mutagens
to
increase the chance of mutations, with
luck a few mutants may have desirable
mutations.


Bacteria:

Genetic Engineering




What is genetic engineering?



-
the process of isolating a desired
gene from the DNA of one organism and
transferring it to the DNA of another
organism.

Genetic Engineering




What are some applications of
genetic engineering?

-
Medicines, vaccines, gene therapy,
agriculture,

Genetic Engineering




How does genetic engineering
work?

-
Genetic engineering experiments
use different approaches , but most
share 4 or 5 basic steps……….

Step 1
-

Cutting DNA


DNA is cut with
restriction enzymes

to
isolate a particular gene. The
RE

recognize
and cut the DNA at a specific sequence
callled a
recognition site
.


This creates
“sticky ends”

or “
blunt ends”
on the gene


pg 251, Figure 12
-
6


Step 2
-

Making the Recombinant DNA


The particular gene that has been cut out is
inserted into plasmid DNA. This is called the
“gene of interest”
.










(Gene of interest)

What is a plasmid??

Step 2
-

Making the Recombinant DNA



Vectors

are used to carry gene of interest to
another cell. Some examples of vectors are:
viruses, yeast and plasmids.


DNA Ligase

is added to help bond the DNA
together.


Recombinant DNA

has DNA from 2 different
species or cells.


Pg 253, Fig. 12
-
8

(Gene of interest)


Step 3
-

Inserting the DNA into a Cell


Recombinant DNA is then put


back into bacterial cells by:


Salt solution via osmosis


Microinjection with glass


needles.


DNA fused to wire pellets


and shot at DNA with a


microscopic gun.






Video on Gene Transfer

Step 4
-

Gene Cloning


In a process called gene
cloning, many copies of
the gene of interest are
made each time the host
cell divides.


Bacteria cells:
accomplished by a process
called binary fission

Cloning
-

(made easy)

Cloned
Animals
-

Makes it possible to
produce large numbers of
identical

organisms with
favorable genetic
characteristics.

Hundreds of cloned animals
exist today, but the number
of different species is
limited. Attempts at cloning
certain species such as
monkeys, chickens, horses,
and dogs, have been
unsuccessful.





Celebrity Sheep Has Died at Age 6





Dolly, the first mammal to be cloned from adult
DNA, was put down by lethal injection Feb. 14,
2003. Prior to her death, Dolly had been suffering
from lung cancer and crippling arthritis. Although
most Finn Dorset sheep live to be 11 to 12 years of
age, postmortem examination of Dolly seemed to
indicate that, other than her cancer and arthritis,
she appeared to be quite normal. The unnamed
sheep from which Dolly was cloned had died
several years prior to her creation. Dolly was a
mother to six lambs, bred the old
-
fashioned way.

Can organs be cloned for use in
transplants?



Scientists hope that one day cloning can be used to
generate tissues and organs for transplants. To do
this, DNA would be extracted from the person in
need of a transplant and inserted into an
enucleated egg. After the egg containing the
patient's DNA starts to divide, embryonic stem cells
that can be transformed into any type of tissue
would be harvested. The stem cells would be used
to generate an organ or tissue that is a genetic
match to the recipient. In theory, the cloned organ
could then be transplanted into the patient without
the risk of tissue rejection. If organs could be
generated from cloned human embryos, the need
for organ donation could be significantly reduced.

Step 5
-

Screening


Cells that have received the particular
gene of interest are distinguished from
the cells that did not take up the vector
with the gene of interest.


Examples: glowing cells, antibiotic
resistant bacteria

Step 5
-

Screening

Gene splicing
-
overview

Insertion
-

microinjection

Insertion
-

microinjection

Insertion and screening

Transgenic Organisms


Transgenic: have foreign DNA


Transgenic Bacteria:
ex:

insulin, growth
hormone, interferon and blood clotting factor.




Transgenic Plants:
ex: insecticides,
fertilizer, resistance to harsh environmental
conditions and viruses, glowing plants??

Organism

Modification

Long life tomatoes

There are two well
-
known projects, both affecting the gene for the
enzyme

polygalactourinase (PG), a pectinase that softens fruits as they
ripen. Tomatoes that make less PG ripen more slowly and retain more
flav
our. The American “Flavr Savr” tomato used antisense technology to
silence the gene, while the British Zeneca tomato disrupted the gene.
Both were successful and were on sale for a few years, but neither is
produced any more.

Insect
-
resistant
crops

Genes
for various powerful protein toxins have been transferred from the
bacterium
Bacillus thuringiensis
to crop plants including maize, rice and
potatoes. These
Bt toxins
are thousands of times more powerful than
chemical insecticides, and since they are built
-
in to the crops, insecticide
spraying (which is non
-
specific and damages the environment) is
unnecessary.

Virus
-
resistant
crops

Gene for virus coat protein has been cloned and inserted into tobacco,
potato and tomato plants. The coat protein seems to “i
mmunise” the
plants, which are much more resistant to viral attack.

Herbicide resistant
crops

The gene for resistance to the herbicide BASTA has been transferred
from
Streptomyces
bacteria to tomato, potato, corn, and wheat plants,
making them resistant t
o Basta. Fields can safely be sprayed with this
herbicide, which will kill all weeds, but the crops. However, this means
using more agrochemicals, not less.

Pest
-
resistant
legumes

The gene for an enzyme that synthesises a chemical toxic to weevils has
be
en transferred from
Bacillus
bacteria to The
Rhizobium
bacteria that live
in the root nodules of legume plants. These root nodules are now resistant
to attack by weevils.

Nitrogen
-
fixing
crops

This is a huge project, which aims to transfer the 15
-
or
-
so g
enes required
for nitrogen fixation from the nitrogen
-
fixing bacteria
Rhizobium
into
cereals and other crop plants. These crops would then be able to fix their
own atmospheric nitrogen and would not need any fertiliser. However, the
process is extremely co
mplex, and the project is nowhere near success.

Crop improvement

Proteins in some crop plants, including wheat, are often deficient in
essential amino acids (which is why vegetarians have to watch their diet
so carefully), so the protein genes are being
altered to improve their
composition for human consumption.


Transgenic Animals:
ex: growth hormone
gene inserted in cattle and fish, farm animals
resistant to certain diseases.

Would it be

Gene Products



The biggest and most successful kind of genetic engineering is the production of gene products.
These products are of medical, agricultural or commercial value. This table shows a few of the
examples of genetically engineered products that
are already available.



Product

Use

Host Organism

Insulin

human hormone used to treat diabetes

bacteria /yeast

HGH

human growth hormone, used to treat dwarfism

bacteria

BST

bovine growth hormone, used to increase milk yield of
cows

bacteria

Factor
VIII

human blood clotting factor, used to treat haemophiliacs

bacteria

Anti
-
thrombin

anti
-
blood clotting agent used in surgery

goats

Penicillin

antibiotic, used to kill bacteria

fungi / bacteria

Vaccines

hepatitis B antigen, for vaccination

yeast

A
AT

enzyme used to treat cystic fibrosis and emphysema

sheep


-
glucosidase

enzyme used to treat Pompe’s disease

rabbits

DNase

enzyme used to treat CF

bacteria

rennin

enzyme used in manufacture of cheese

bacteria /yeast

cellulase

enzyme used in paper production

bacteria

PHB

biodegradable plastic

pla
nts


Some transgenic info.


In 2003, about 167 million acres grown by 7
million farmers in 18 countries were planted with
transgenic crops, the principal ones being
herbicide
-

and insecticide
-
resistant soybeans,
corn, cotton, and canola. Other crops grown
commercially or field
-
tested are a sweet potato
resistant to a virus that could decimate most of
the African harvest, rice with increased iron and
vitamins that may alleviate chronic malnutrition in
Asian countries, and a variety of plants able to
survive weather extremes.


On the horizon are bananas that produce human
vaccines against infectious diseases such as
hepatitis B; fish that mature more quickly; fruit
and nut trees that yield years earlier, and plants
that produce new plastics with unique properties.

Genetically Modified (transgenic) Products


Benefits


Crops



Enhanced taste and quality


Reduced maturation time


Increased nutrients, yields, and stress tolerance


Improved resistance to disease, pests, and herbicides


New products and growing techniques


Animals



Increased resistance, productivity, hardiness, and feed efficiency


Better yields of meat, eggs, and milk


Improved animal health and diagnostic methods


Environment



"Friendly" bioherbicides and bioinsecticides


Conservation of soil, water, and energy


Bioprocessing for forestry products


Better natural waste management


More efficient processing


Society



Increased food security for growing populations


GM products


Controversies


Safety



Potential human health impact: allergens, transfer of antibiotic
resistance markers, unknown effects Potential environmental impact:
unintended transfer of transgenes through cross
-
pollination, unknown
effects on other organisms (e.g., soil microbes), and loss of flora and
fauna biodiversity


Access and Intellectual Property



Domination of world food production by a few companies


Increasing dependence on Industralized nations by developing countries


Ethics



Violation of natural organisms' intrinsic values


Tampering with nature by mixing genes among species


Objections to consuming animal genes in plants and vice versa


Stress for animal


Labeling



Not mandatory in some countries (e.g., United States)


Mixing GM crops with non
-
GM confounds labeling attempts


Society



New advances may be skewed to interests of rich countries

DNA Sequencing

Human Genome Project

A map of a
portion of a
human
chromsome

DNA Sequencing


Sequencing is figuring out the code of
specific genes. After time, finding out
code for an entire organism.


Many copies of DNA needed (cloning)


Radioactive Label


Gel Electrophoresis, Fig.12
-
9





Video on Genetic Engineering Applications

DNA Fingerprinting

•1985
-

Alec Jeffreys introduced DNA fingerprinting.
It is based on the fact that no two people (except
identical twins), have the same DNA fingerprint.

•Uses: criminal investigations, paternity, rape cases,
etc.

•Very small amounts of DNA are needed, taken
from blood, saliva,hair, urine, etc.


DNA Fingerprinting

Making A DNA fingerprint

1.
DNA is cut by restriction enzymes at specific
recognition sites.

2.
DNA is micro
-
pipetted into the wells.

3.
An electric current moves the DNA across the
gel.


-
DNA has a neg. charge and will travel towards
the pos. end of the gel


-
small fragments of DNA will travel further.

4. The DNA bands are compared.



DNA

Fingerprinting

Gel Electrophoresis

DNA

Fingerprinting

PCR
-

polymerase chain reaction

Gene Therapy