Biology Chapter 12

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14 Δεκ 2012 (πριν από 4 χρόνια και 9 μήνες)

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©
The McGraw
-
Hill Companies, Inc. Permission required for reproduction or display.

Chapter 12

Biotechnology
and Genomics


Cloning


Cloning
-

the production of genetically
identical copies of DNA, cells, or
organisms through asexual means


(i.e., single parent)


Plants are Cloned from a Single Cell

Cloning Carrots

Animals are Cloned Using

a Donor Nucleus


Reproductive cloning
produces individual
that are a genetic copy of the original


Therapeutic cloning

produces mature cells
of various cell types


Purposes of therapeutic cloning


learn more about how specialization of cells
occurs


provide cells and tissues that could be used
to treat human illnesses

Reproductive Cloning

Therapeutic Cloning

Animal Cloning has Benefits and
Drawbacks


First mammal to be successfully cloned
was Dolly, the sheep


Since Dolly, mice, cats, dogs, and monkeys
have been cloned


Animal Cloning has Benefits and
Drawbacks


Cloning Benefits


increases knowledge of gene interactions and
embryological development


may be the only way to save endangered
species


can be used to repair organs


combat cancer


fight disease


Animal Cloning has Benefits and
Drawbacks


Cloning Drawbacks


because the donor’s mitochondrial DNA is not
passed to the clone, premature aging may
occur


the “age” of the donor’s telomeres may also
cause premature aging


can concentration genetic defects


mutation rate is higher in clones


regulation of gene expression is abnormal


may create ethical issues



DNA can be Isolated and Cloned

Gene Cloning
-

produces many identical
copies of the same gene


Requires
recombinant DNA (rDNA)

which
has DNA from one or more different sources


To create rDNA a
vector

is used to introduce
DNA into a host cell, which is often a
bacterium


One common vector is a
plasmid,
a small
non
-
chromosomal piece of DNA found in
bacteria

Cloning

a

Gene

Cloning

a

Gene

Specific DNA Sequences can be Cloned


Polymerase Chain Reaction (PCR)

can
create copies of a segment of DNA quickly
in a test tube


Commonly used to amplify small
amounts of DNA

Copies of DNA

segments
produced

per PCR cycle
per

one original
strand

Specific DNA Sequences can be Cloned


DNA Fingerprinting

detects how many
times a short sequence is repeated


People differ by how many repeats they have
at particular locations

DNA fingerprinting of specific base repeat units at
different genome locations establishes paternity:

Male 1 is the father

Bacteria can be Genetically Modified to
Make a Product or Perform a Service


Organisms are genetically modified (GM)
in order to produce specific products


These are called transgenic organisms


They produce
biotechnology products


Example
: insulin, human growth hormone,
and hepatitis B vaccine

Making Cheese via Genetic Engineering


Cheese
-
making industry was dependent
upon rennet, which consists of two
enzymes: chymosin and bovine pepsin


Traditionally, rennet was collected from the
stomach lining of calves, but it became
scarce as veal industry declined

Making Cheese via Genetic Engineering


Gene responsible for formation of
chymosin was isolated from calf cells,
cloned and inserted into the genome of
several organisms


Cheese containing chymosin was the first
food dependent on genetic engineering in
U.S. history

Plants are Genetically Modified to Increase
Yield or to Produce a Product

Corn, potato, soybean, and cotton plants
have been engineered to be resistant to
insect predation or widely used herbicides


Crops with other improved agricultural and
food
-
quality traits are desirable


Soybeans have been developed that mainly
produce the fatty acid oleic acid, a change
that may improve human health

Genetically modified


crops of the future

Are Genetically Engineered Foods Safe?


FDA study
-

most people believe genetically
engineered foods might offer benefits, but feared
unknown long
-
term health consequences


Scientists are concerned about the potential
drawbacks to the planting of GM corn


Resistance among populations of the target pest


Exchange of genetic material between the transgenic crop
and related plant species


GM crops’ impact on nontarget species


Nonetheless, USDA reports that U.S. farmers in 2004
planted genetically engineered corn on 45% of all
corn acres

Animals are Genetically Modified to

Enhance Traits or Obtain Useful Products

Xenotransplantation
is the use of animal
organs, instead of human organs, in
transplant patients


Pigs genetically modified so their organs are
less likely to be rejected by humans?

A procedure
for producing
many female
clones that
yield the same
product

GM mice showed

that male gender
is due to

SRY

DNA

A Person’s Genome can be Modified


Gene Therapy
-

insertion of foreign gene into
human cells for treatment of a disorder


Ex Vivo Gene Therapy


To treat SCID, bone marrow stem cells are removed
from the patient and infected with a virus that carries
a normal gene for the enzyme


In Vivo Gene Therapy


The gene needed to cure cystic fibrosis is sprayed
into the nose or delivered to the lower respiratory
tract by a virus or by liposomes


Limited success for these so far.

Sites of
ex vivo
and
in vivo
gene
therapy to cure
the conditions
notes

Gene Therapy Trials have Varying
Degrees of Success

Severe Combined Deficiency Syndrome (SCID)


Children able to soon go home


After three years, 3 of the 10 children developed
leukemia and needed chemotherapy


Skin Cancer


The skin cancer melanoma accounts for only
about 4% of skin cancer cases, but it is also the
most serious and most aggressive type.


After one year, 2 of 15 patients remained disease
-
free.


A procedure for
modifying the
white blood cells
to fight cancer

The Human Genome Sequence

Human Genome Project (HGP)
-

determined the order of the 3 billion bases
in our
genome
(all of

our genes)


How did they do it?


Developed a laboratory procedure to analyze
a short sequence of base pairs


Instruments were developed that increased
automation


The Human Genome Sequence

Many small regions of DNA that vary among
individuals were identified during the HGP


Most of these are
single nucleotide
polymorphisms (SNPs)


Personal Genome Project


Sequence every person’s genome


Possible benefits and drawbacks?



New Cures on the Horizon?

Possibility A: Many new medicines


Now researchers can take a more systematic
approach to finding effective medicines


Possibility B: Medicines will be safer due
to genome scans


Use of a gene chip will quickly and efficiently
provide knowledge of your genetic profile


New Cures on the Horizon?

Possibility C: Longer and healthier life


Preembryonic gene therapy may become
routine once we discover the genes that
contribute to a longer and healthier life


Possibility D: Design your children


It may be possible to cure genetic disorders
before a child is born by adding a normal gene
to any egg that carries a mutant gene

Therapeutic Use of Stem Cells

Stem Cell

2010



use of 11 yr old boys own stem cells

to rebuild damaged trachea

Proteomics and Bioinformatics are New
Endeavors

Proteome


collection of all proteins in the
organism


Proteomics
is the study of the structure,
function, and interaction of cellular proteins

Proteomics and Bioinformatics are New
Endeavors

Bioinformatics
is the application of
computer technologies to the study of the
genome


Scientists hope to find cause
-
and
-
effect
relationships between various genetic profiles
and genetic disorders caused by multifactorial
genes

Summary

Research into the nature and organization of
genes in various organisms allowed
geneticists to produce recombinant DNA


A knowledge of transcription and
translation enables scientists to
manipulate the expression of foreign
genes in organisms


Summary

These breakthroughs have spurred a
biotechnology revolution


Bacteria and eukaryotic cells are now
used to produce vaccines, hormones,
and growth factors for use in humans

Summary

Although some people are fearful about the
consequences of biotechnology on
ecological and human health, no serious
problems have surfaced thus far


Biotechnology offers the “promise” of
curing some human genetic disorders,
such as muscular dystrophy, cystic
fibrosis, hemophilia, and many others