Chapter 13 – Genetic Engineering

butterbeanscubaBiotechnology

Dec 12, 2012 (4 years and 11 days ago)

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Chapter 13


Genetic
Engineering

L2 Biology

Has Bonnie been bred by selective breeding?

Selective Breeding


Choose organisms with the desired traits
and breed them, so the next generation also
has those traits


Nearly all domesticated animals and crops


Luther Burbank (1849
-
1926) developed
>800 diff varieties of plants in his lifetime






Hybridization



Breed two dissimilar organisms


In plants


often results in better lines


hybrids are larger, stronger,
etc


In animals


hybrids produced may be weaker and sterile


Ex


wolf x dog
----

weak wolf
-
dog


Ex


horse x donkey
----

mule (sterile)

Horse x Donkey = Mule

Lion x Tiger = Liger


Inbreeding


Breeding two organisms that are


very similar to produce offspring


with the desired traits.


Ex


dog breeds



Risks



might bring together two
individuals that carry bad recessive genes


many purebred dogs have genetic disorders
that mutts don’t get.

Increasing Variation


Induce mutations


the ultimate source of
genetic variations among a group of
organisms


Mutagens used


radiation and chemicals


Some organisms are formed that have more
desirable variations.

Producing new kinds of bacteria


Can expose millions of bacteria at one time
to radiation


increases chances of
producing a successful mutant.


Ex


bacteria that can digest oil have been
produced this way







Producing new kinds of plants:


Drugs that prevent chromosomal separation
in meiosis have been used to create plants
that have more than two sets of
chromosomes (2n). These are called
polyploid plants.


Ex


bananas, citrus fruit, strawberries, many
ornamental flowers





Diploid corn

Tetraploid corn

Manipulating DNA


tools of the
molecular biologist


DNA extraction


open the cells and
separate DNA from all the other cell parts.


Remember the kiwi lab?


Cutting DNA


Use restriction enzymes




each one cuts DNA at a


specific sequence of nucleotides.


This will make different


lengths of DNA


Separating DNA


Gel Electrophoresis


Place fragments at one end of a porous gel


we
use agarose gel


Apply an electric current


The DNA is
negatively charged and will travel toward the
positive end of the gel.


The larger pieces of DNA move slower, the
smaller ones faster.


Used to compare genomes of different
organisms or different individuals.


Also used to locate and identify one particular
gene out of an individual’s genome.

Click here for animation about
gel electrophoresis

Using the DNA Sequence


Sequence can be read, studied, and changed.


Techniques used to study DNA sequences:


Use DNA polymerase and the 4 DNA bases to
produce a new DNA strand complementary to
unknown strand


some of the bases are dyed.


Dye
-
labeled strands are then separated using gel
electrophoresis and the order of the bands tells the
DNA sequence of the unknown strand.


Cutting and Pasting


make recombinant DNA (DNA from
two different organisms).


Cut out the gene to be inserted, use same restriction
enzyme to cut the receiving DNA strand, attach the two
DNA strands





Making Copies


Polymerase Chain Reaction (PCR) is used
to make many copies of the same piece of
DNA like a photocopy machine makes
copies of papers.


This is useful if there is only a very small
sample of DNA available (as that found in a
small blood drop at a crime scene)

Cell Transformation


A cell takes in DNA from outside the cell
and that DNA then becomes part of the
cell’s DNA.





Bacteria


place DNA in the solution that
bacteria live in, and some of that DNA will
be taken in by the bacteria cells.

Bacteria Transformation using
Recombinant DNA


Cut a gene with a restriction enzyme out of a
human cell (ex


gene for insulin or growth
hormone work well)


Cut a bacterial plasmid using the same restriction
enzyme (DNA ends will be complementary)


Insert Human gene into bacterial plasmid


Insert plasmid back into bacterial cell


Bacteria will multiply, and all offspring will have
that gene


these bacteria will then follow the
directions of the human gene and make the protein
coded for (insulin or human growth hormone)


Transforming Plant Cells




Use bacterial plasmid to insert desired gene
into DNA of a plant

Transforming Animal Cells


Directly inject DNA into the nucleus of an egg


it will become part of the chromosomes.


Has been used to replace specific genes.







Glowing mouse cells in
embryos that were made
from sperm given the gene
for bioluminescence from
jellyfish


now all the cells
glow!

Applications of Genetic
Engineering


Gene for luciferase was isolated from
fireflies and inserted into tobacco plants


they glowed!


Transgenic organisms


contain genes from
other species

A transgenic mouse,
which carries

a jellyfish gene,
glows green under

fluorescent light.




Transgenic Organisms


Bacteria
-

Make human proteins like insulin


Plants


52% of soybeans, 25% of corn in
US in year 2000. Some produce natural
insecticide, some resist weed
-
killers, may
soon be used to produce human antibodies;
rice with vitamin A.



Animals


mice
with immune
systems like
humans; farm
animals that grow
faster and larger
with extra copies of
growth hormone
genes; animals with
leaner meat;
chickens resistant to
bacterial infections.





Cloning


Clone



member of a population


of genetically identical cells


produced from a single cell.




1996


Dolly

cloned




1
st

mammal (sheep) cloned.


She got arthritis several years


earlier than most sheep


Died in 2003