Genetic engineering - Quia

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14 Δεκ 2012 (πριν από 4 χρόνια και 10 μήνες)

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CHAPTER
13

Genetic Engineering

13
-
1 Changing the Living World

Selective Breeding
-

allowing only those animals
with desired characteristics to produce the next
generation


ex: different dog breeds


Selective Breeding


Selective breeding uses genetic
variation in organisms to pass
desired traits onto the next
generation.


Luther Burbank
(1849
-
1926)


Created 800 varieties of plants


Disease resistant Burbank potato
-

which was used in Ireland to fight
potato blight

Hybridization


Hybridization
-

crossing dissimilar individuals to
bring together the best of both organisms


Hybrids are often stronger than either parent


Ex: crossing disease resistance with food producing
capacity

Inbreeding


Inbreeding
-

continued breeding of individuals
with desired characteristics


Used to maintain desired characteristics of a line



Problems: greater chance of having two recessive
alleles for a genetic defect.


Ex: dog breeds that have joint problems and
blindness

Increasing Variation


Breeders can increase the genetic variation in a
population by inducing mutations



Example: creating bacteria that can digest oil and
clean up an oil spill


Polyploid

plants
-

are usually stronger and larger

13
-
2 Manipulating DNA

The tools of molecular biology


Genetic engineering
-

making changes to the DNA
of an organism


What is possible with genetic engineering?

Are there any ethical or moral considerations?


DNA extraction
-

cells are
lysed

(broken) and the
DNA is separated from the other cell parts


Cutting DNA
-

restriction enzymes will cut DNA
at a certain location


Restriction enzymes comes from bacteria that use
them to protect against foreign DNA

Restriction Enzymes create
sticky ends (ends of a
DNA that can bind to
other DNA fragments)



Separating DNA
-

done by Electrophoresis



Electrophoresis
-

separating DNA fragments
based on size by using electricity


DNA is slightly negative
-

it will travel to a
positive charge


DNA is cut into small fragments


The DNA goes through a matrix (
agarose

or
acrylamide
)


The smaller fragments travel faster


Ethidium

bromide can be added to see the DNA
fragments with UV light






Using the DNA sequence

Reading the DNA sequence (DNA sequencing)

DNA is put into a tube with DNA polymerase

Nucleotides are added to the tube

Some of the nucleotides have a tag. If these
nucleotides are added to
DNA then
it stops
replicating.

The tag can be radioactive or a florescent dye.




Recombinant DNA
-

combining DNA from
different sources


Two different organisms


Natural DNA with artificially created DNA

PCR Polymerase Chain Reaction


PCR
-

process of copying a certain segment of
DNA. The segment is copied many times.


Taq

polymerase
-

copies DNA, does not denature
at high temperatures


Primer
-

short segment of DNA used to begin
replication


Developed by
Kary

Mullis






13
-
3 Cell Transformation


Transformation
-

a cell takes in foreign DNA.
This DNA is expressed (transcribed and
translated) by the cell.


Plasmid
-

small, circular segment of DNA



Plasmids are useful in transformation.





Transformation


Genetic marker
-

something that distinguishes
organisms with a certain DNA



Antibiotic resistance is a common genetic marker

Transforming plant cells


A bacteria can infect a plant and transfer its DNA
to the plant cells.



1. A certain gene is put into a plasmid.


2. The bacteria is transformed to accept the
plasmid.


3. The bacteria infects the plant.


4. The plant now has the inserted gene and
incorporates it into its chromosomes.


Transforming animal cells


Animal cells can be transformed


1. Inject DNA directly into an egg


2. Use a vector (virus) to transfer DNA into a cell

13
-
4 Applications of Genetic Engineering


Luciferase
-

enzyme that allows fireflies to glow


Luciferase

gene was inserted into a plant


The plant glowed

Transgenic Organisms


Transgenic
-

organisms that have genes from
other species



Transgenic bacteria
-

produce human insulin,
growth hormone, and clotting factor


Advantages: bacteria reproduce quickly and are easy to
grow

Transgenic animals



Mice are given human genes for their immune system
to study the effect of various diseases


Livestock are given extra copies of growth genes to
grow faster


Some animals are given genes to produce certain
human proteins.


Organ donation?

Transgenic plants


In 2000, 52% of soy and 25% of corn grown in
the US was genetically modified (GM)


Modified to produce an insecticide and resist
weed
-
killing chemicals


Other possible modifications: rice with extra
Vitamin A



Should we genetically modify our plants and
animals?


What are the risks or rewards?

Cloning


Clone
-

an exact genetic copy of another organism



Do clones exist naturally?

Is cloning useful?


Why would you want to clone an animal?



1997, Ian
Wilmut

cloned a sheep, “Dolly”



Cows, pigs, mice and other mammals have also
been cloned



1. Cells taken from donor


2. An egg from a second
donor has its nucleus
removed


3. DNA from first donor
is inserted into the egg of
the second donor


4. The egg is grown and
inserted into a surrogate
mother


5. Clone is born