Biotechnology

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11 Δεκ 2012 (πριν από 4 χρόνια και 11 μήνες)

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Biotechnology

Chapter 10


10.1
Impacts/Issues

Golden Rice or Frankenfood?



Genes from one species may be inserted into an individual of another species


or a
gene may be modified and reinserted into an individual of the same species


Golden Rice



Rice plan
ts with added genes make and store beta carotene




Transgenic



An organism that has been genetically modified with genes from a different species




Genetically modified organisms

(GMOs)



Organism whose genome has been modified by genetic engineering


10.2 F
inding Needles in Haystacks



Gene research was limited until enzymes produced by bacteria to cut viral DNA were
discovered




Restriction enzyme



Enzyme that cuts DNA at specific base sequences



Used in DNA cloning to cut DNA into pieces that are inserted into

cloning vectors


DNA Cloning



DNA cloning mass
-
produces DNA fragments for research




DNA cloning



Set of procedures that uses living cells to make many identical copies of a DNA
fragment




Clone



A genetically identical copy of DNA, a cell, or an organism


Clo
ning Vectors



Cloning vector



A DNA molecule that can accept foreign DNA, resulting in a hybrid molecule that
can be transferred to a host cell, and get replicated in it




Plasmid



A small, circular DNA molecule in bacteria, replicated independently of the
chr
omosomes



A cloning vector


Recombinant DNA



Recombinant DNA molecules are introduced into host cells such as bacteria, which
copy the DNA as they divide




Recombinant DNA



Contains genetic material from more than one organism


Making Recombinant DNA

1. A rest
riction enzyme recognizes specific base sequences in DNA from two different
sources

2. Restriction enzymes cut DNA into fragments with single
-
stranded tails (“sticky ends”)

3. DNA fragments from different sources are mixed together; matching sticky ends ba
se
-
pair

4. DNA ligase joins fragments, forming recombinant DNA


Commercial Plasmid Cloning Vector

cDNA Cloning



RNA cannot be cloned directly; reverse transcriptase is used to copy single
-
stranded
RNA into cDNA for cloning




Reverse transcriptase



Viral enz
yme that uses mRNA as a template to make a strand of DNA




cDNA



DNA synthesized from an RNA template by the enzyme reverse transcriptase


Libraries



A library is a collection of cells that host different fragments of DNA, often
representing an organism’s ent
ire genome



Researchers make DNA libraries to isolate one gene from the many other genes in a
genome




Genome



An organism’s complete set of genetic material


Nucleic Acid Hybridization



Probes are used to identify one clone that hosts a DNA fragment of intere
st among
many other clones in a DNA library




Probe



Short fragment of DNA labeled with a tracer



Hybridizes with a specific nucleotide sequence




Nucleic acid hybridization



Base
-
pairing between DNA or RNA from different sources


PCR



PCR quickly mass
-
produces
copies of a particular DNA fragment for study




Polymerase chain reaction (PCR)



Uses primers and heat
-
resistant DNA polymerase to rapidly generate many copies
of a DNA fragment




Primer



Short, single
-
strand of DNA designed to hybridize with a DNA fragment


S
teps in PCR

1. Starting material is mixed with DNA polymerase, nucleotides and primers

2. Mixture is heated and cooled in cycles



At high temperature, DNA unwinds



At low temperature, primers base
-
pair with template DNA

3.
Taq

polymerase synthesizes compleme
ntary DNA strands on templates


10.3 Studying DNA



Short tandem repeats are multiple copies of a short DNA sequence that follow one
another along a chromosome



The number and distribution of short tandem repeats, unique in each individual, is
revealed by el
ectrophoresis as a DNA fingerprint


DNA Fingerprinting



DNA fingerprinting is used in forensics, court evidence, and other applications




DNA fingerprint



An individual’s unique array of short tandem repeats




Electrophoresis



Used to separate DNA fragments by
size


The Human Genome Project



Automated DNA sequencing and PCR enabled scientists to sequence the more than 3
billion bases of the human genome




Sequencing



Method of determining the order of nucleotides in DNA


Sequencing a Fragment of DNA



The order of co
lors is the order of DNA bases (A, T, G, C)


Genomics



Analysis of the human genome sequence is yielding new information about human
genes and how they work




Genomics



The study of genomes (structural genomics, comparative genomics)


10.4 Genetic Engineerin
g



Recombinant DNA technology and genome analysis are the basis of genetic
engineering



Genetic engineering is the directed alteration of an individual’s genome, resulting in a
genetically modified organism (GMO)




Genetic engineering



Process by which deliber
ate changes are introduced into an individual’s genome


Genetically Modified Microorganisms



A transgenic organism carries a gene from a different species



Transgenic organisms are used in research, medicine, and industry



Transgenic bacteria and yeast produc
e medically valuable proteins


Designer Plants



Transgenic crop plants help farmers produce food more efficiently



Plants with modified or foreign genes are now common in farm crops


Using the Ti plasmid

to Make a Transgenic Plant

Animation: Gene transfer
using a Ti plasmid


Genetically Modified Crops



Bt

gene confers insect resistance to corn


Biotech Barnyards



Transgenic animals produce human proteins



Animals that would be impossible to produce by traditional breeding methods are
being created by genetic

engineering




Transgenic animals are used in research, medicine, and industry


Transgenic Animals

Knockout Cells and Organ Factories



Transgenic animals may one day provide a source of organs and tissues for
transplantation into humans




Xenotransplantation



Transplant of an organ from one species to another


10.5 Genetically Modified Humans



Genes can be transferred into a person’s cells to correct a genetic defect or treat a
disease



However, the outcome of altering a person’s genome remains unpredictable




Gen
e therapy



Transfer of a normal or modified gene into an individual with the goal of treating a
genetic defect or disorder


Unpredictable Outcomes



There are more than 15,000 serious genetic disorders


gene therapy is the only real
cure



In some cases, gene

therapy works


in other cases it leads to death



Inserting a virus
-
injected gene into a chromosome can disrupt normal function and
cause cancer



Severe allergic reaction to the viral vector can cause death


One Successful Case of Gene Therapy



Rhys Evans,
born with a severe immune disorder (SCID
-
X1) received a normal gene
and no longer lives in isolation


Getting Perfect



Eugenics



Idea of deliberately improving the genetic qualities of the human race



The potential benefits of genetically modifying humans mus
t be weighed against the
potential risks, including social implications


10.6
Impacts/Issues

Revisited



Golden rice with beta carotene was ready for distribution in 2005 but is still not
available for human consumption


the biosafety experiments required a
re too
expensive for the public humanitarian agency that developed it