Genetic Engineering - CBraun

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16 Δεκ 2012 (πριν από 4 χρόνια και 7 μήνες)

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Genetic Engineering

Selective Breeding

&

Increasing Variation

Selective

Breeding


HUMANS

cross parents with desired traits


offspring with desired traits (flower color,
disease resistance, increased milk production)


Dogs and cats, farm animals, crop plants

Selective Breeding

Hybridization



Cross dissimilar
individuals


best of both


Ex. Disease resistance with
food producing capacity


Dogs?

Inbreeding


Maintain desired traits


Cross similar individuals


Genetically similar
individuals breeding


increase chance for two
recessive alleles


Defects can result; ex
dogs

blindness, leg
deformity,
blue
Fugates

of
KY

Increasing Variation


Breeders use
mutagens
to cause mutations


ultimate source of genetic variation


Some mutations unique and desirable


Ex: chemicals and
radiation

oil
-
eating
bacteria!


Polyploidy in plants

larger, stronger than 2n

Manipulating DNA


Change DNA!


extract


cut


identify gene sequences


make unlimited copies


recombine


DNA extraction

chemical (ex. strawberry)


Cut

restriction enzymes
cut DNA at specific
sequences (chemical scissors)


Fragments


Plasmids (circular DNA in bacteria)

Different restriction enzymes cut DNA in
different ways.


each enzyme has a different restriction site
(lock and key)


Restriction Sites


some cut straight across and leave “blunt
ends”


some make staggered cuts and leave “sticky
ends”


Gel electrophoresis


Separates DNA
fragments by size:


DNA sample is cut with
restriction enzymes


Electrical current pulls
DNA fragments through
gel (“JELLO swimming”)


Smaller fragments move
faster, travel farther than
larger fragments


Fragments of different
sizes appear as bands on
the gel


DNA Fingerprinting

DNA fingerprints identify people at the
molecular level.


evidence in criminal cases


paternity tests


studying biodiversity



tracking genetically


modified crops



DNA fingerprinting depends on the probability of a
match.


Many people have the

same number of

repeats in a certain

region of DNA.


The probability that two

people share identical

numbers of repeats in

several locations is

very small.


(mother) (child 1) (child 2) (father)

The Crime


On the evening of November 1, at approximately 8:15 p.m.,
Jimmy Sweet entered his bedroom, walked over to his desk,
and sat down at his computer. While reaching for the
computer's switch he noticed, out of the corner of his eye,
that one of the items on a typically well
-
organized shelf was
out of place.


Jimmy shot across the room for a closer examination. Sure
enough, the object in question had indeed been disturbed.


The object had been sealed in an air
-
tight package. The
package was now ripped open. The object was still inside,
but it was no longer in its original condition. In Jimmy's eyes,
it was now worthless.


Jimmy pulled out what had been his most
-
valued possession
--

his lollipop. The confectionery treat was now a sticky
mess. Someone had obviously indulged him
-

or herself in its
sugary molecules.

Create the Fingerprint

Analyze the Fingerprint

Choose the Culprit


http://www.pbs.org/wgbh/nova/sheppard/an
alyze.html




Cell Transformation


Organism’s DNA can be
changed

new

traits


New
genes can be added


Recombinant
DNA

genes
from

more than one


organism.


(bacterial DNA)


Bacterial plasmids
used
to
make recombinant DNA.


plasmids are loops of DNA in
bacteria


restriction enzymes cut plasmid
and foreign DNA


foreign gene inserted into
plasmid



Transgenic organism
--
one
or more genes from
another organism inserted into its
genome
and TURNED ON (expressed)



Transgenic bacteria
produce
human
proteins:


Human gene spliced into bacteria DNA


Bacteria
express the
gene


Insulin, human growth hormone


Transgenic plants
are common in
agriculture:


Transgenic bacteria infect
a
plant and plant expresses gene


Many
crops

now genetically modified (
GM
)


Produce own insecticide,

Fertilizer, resist freezing


Luciferase


tobacco???


Transgenic animals
are used to study diseases
and gene
functions:


Human immune system and HIV in mice


Hardier livestock



Concerns
about
uses
of genetic
engineering:


possible long
-
term health effects of eating GM
foods


possible effects of GM plants on ecosystems and
biodiversity


Clone

--
genetically
identical copy of a
gene
or
organism
.


Dolly 1997 (Ian
Wilmut
)


Cloning
in
nature (asexual reproduction)


bacteria (binary fission)


plants (strawberries

vegetative propagation)


simple
animals (budding, regeneration)



Mammals cloned via
nuclear transfer
:


nucleus
(n) is
removed from an egg cell


nucleus
(2n) of
a cell from the animal to be cloned
is implanted in the egg



Cloning
potential
benefits:


Organs for transplant into humans


Save endangered species




Cloning
concerns:


Low success rate


Clones “imperfect” and less healthy than original
animal


telomeres


Decreased biodiversity


What does it mean for
Homo sapiens?


Human Genome Project

sequence and
analyze entire human DNA sequence


Locate and identify specific genes


Gene

Therapy

potential to replace absent or
faulty genes with normal working genes


Imagine: What will a biology
classroom or doctor visit look like
in 30 years?