Chapter 13 Genetic Engineering - papbiobellaire

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

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Chapter 13

Genetic Engineering

Glow in the Dark, oil eating
bacteria; clones; hybrids…say
what??


Yes, these things are real and possible.


If you could manipulate DNA, what would you
do?


What application would it have for society as a
whole?


What are some of the moral questions that
might arise from your proposed
manipulation?

Changing the Living World

1. Selective Breeding:



Selective breeding


allowing only the
organisms with desired traits to breed


Takes advantage of naturally occurring variation


Ex: domestic dogs, cats, farm animals, most crops


Cont. Selective Breeding



Hybridization


crossing dissimilar
individuals

& bringing together the
best of both organisms


Hybrids usually hardier than either
of the parents


Ex: crossing disease resistance with
food production



Inbreeding


continued breeding
of individuals with similar
characteristics


Increased risk of genetic defects


Ex: maintaining characteristics in
breeds of dogs


Ever wondered what a

human
-
dog hybrid

would look like?!?!

Human
-
Dog hybrid

was a sculpture created by an
Australian artist named
Patricia Piccinini
.

Increasing Variation


Breeders increase variation by
inducing mutations (***
ultimate source of variation
)



New kinds of bacteria
produced by treating them
with chemicals and radiation


-

Results
: bacteria that can
digest oil used to clean up oil
spills


Cont. Increasing Variation


New kinds of plants
produced by treating
them with drugs that
prevent chromosome
separation during
meiosis


-

Results
: polyploidy
cells


plants larger and
stronger

(LETHAL in
animals!)


Manipulating DNA


Genetic engineering


making changes in the DNA code of an
organism



1.
The Tools of Molecular Biology

a.
DNA extraction


open cells and separate DNA from other cell
parts

b.
Cutting DNA

via
restriction enzymes


cut DNA into smaller
pieces at a specific sequence of nucleotides

c.
Separating DNA

via
gel electrophoresis


mixture of DNA
fragments are put in one end of porous gel and an electric
voltage is applied


-

DNA is negatively charged so the fragments begin to travel toward
the positive end of the gel


-

The smaller the fragment, the faster it travels; the larger/slower


Cutting DNA

Recombinant DNA is DNA taken from two different sources and fused into a single DNA molecule.
Special DNA cutting enzymes, called restriction enzymes, cut the DNA at specific sites. Each
restriction enzyme recognizes a different nucleotide sequence. DNA that is cut with a restriction
enzyme will have single
-
stranded ends, called “sticky ends”. Two molecules of DNA cut with the
same restriction enzyme will have the same exposed nucleotides and will undergo complementary
base pairing.

Gel Electropheresis


Electrophoresis

Cont. Manipulating DNA

2.
Using the DNA Sequence



a.
Reading the sequence


use fluorescent dyes
to identify specific bases and DNA sequences


b.
Cutting and pasting

via
recombinant DNA


use restriction enzymes to “cut” a gene form one
organism and using special enzymes (ligase)
“paste” it into the DNA of another organism


c.
Making copies

via
polymerase chain reaction
(PCR)


produces multiple copies of DNA strand


Cell Transformation



1.
Transformation


process in which bacteria or some other organism takes in DNA
from its environment and incorporates it into its own DNA




a. Transforming Bacteria


Plasmids


small circular pieces of DNA

useful for DNA transfer for 2 reasons:



1. Bacterial origin of replication



2. Genetic marker


a gene that makes it possible to identify the


transformed bacteria




Ex: genes for resistance to antibiotics


Cont. Transformation


b. Transforming Plant Cells


Infect plant cells with
recombinant plasmid
whose
tumor producing gene has been inactivated



c. Transforming Animal Cells


Inject DNA directly into the nucleus of an egg cell,
foreign DNA is inserted into the chromosome


Applications of Genetic Engineering


1.
Transgenic Organisms


contain genes from other organisms




a. Transgenic Microorganisms



Bacteria transformed with
human genes
for insulin, growth
hormone, clotting favors etc. produce human products



b. Transgenic Animals


Mice with human immune systems are used to study effects of disease


Livestock with extra copies of growth hormone to produce faster
growth and less fatty meat


c. Transgenic Plants


Genetically modified food (GM)


52% of soy beans and 25% corn


Plants contain genes that produce natural insecticide or weed
resistance


Transgenic Animal: Belgian Blue Cattle


Cloning

1.
Clone


member of a
population of genetically
identical cells produced from a
single cell



Steps:


1. Nucleus of egg cell removed


2. Donor nucleus fused with
egg cell using an

electric shock


3. Fused cell begins to divide


4.
Embryo placed in uterus of
foster mother


Dolly’s Bonnie