Biotechnology and Society

gooseliverΒιοτεχνολογία

22 Οκτ 2013 (πριν από 3 χρόνια και 9 μήνες)

82 εμφανίσεις

Biotechnology and Society

Prof. Arnaldo Ferreira

Keep In Mind




Biotechnology is an outgrowth of recombinant
DNA technology



Biotechnology


The use of recombinant DNA technology to
produce commercial goods and services


14.1 Biopharming: Making Medical
Molecules in Animals and Plants



Genetic engineering is used to manufacture
proteins used in treating human diseases


Examples:

Blood clotting factors, insulin


Provides a constant supply, uncontaminated by
disease
-
causing agents



These proteins are made in bacteria, cell lines
from higher organisms, animals, and plants

Human Proteins

Can Be Made in Animals



Transgenic


The transfer of genes between species



Transgenic organism


An organism that has received a gene from
another species by means of recombinant DNA
technology

Pompe Disease



Pompe disease


An inability to make
α
-
glucosidase (GAA)


Treated by enzyme replacement therapy



Transgenic animals produce human GAA


Transgenic female rabbits produce human GAA
enzyme in their milk


Human GAA produced in transgenic hamster
cells

14.2 Genetically Modified Foods



Gene transfer into crop plants confers resistance
to herbicides, insect pests, and plant diseases


Also used to increase the nutritional value of
foods (such as vitamin A)



Genetically modified organisms (GMOs)



A term referring to transgenic plants or animals

Genetically Modified Foods




60% to 70% of foods in US supermarkets
contain some transgenic plant material



Products made from corn, soybeans, cottonseed
and canola oils most commonly contain
transgenic ingredients

Transgenic Crops

Used to Enhance Nutrition





Golden rice increases vitamin A


Genes from daffodils, corn, and bacteria





Concerns About

Genetically Modified Organisms



Are foods containing new proteins safe to eat?



Is it safe to eat food carrying part of a viral gene
that switches on transgenes?



Will pesticide
-
resistant insects develop?



Will disease
-
causing bacteria acquire antibiotic
-
resistance genes used as markers?

Keep In Mind





Many crop plants have been genetically
modified

14.3 Transgenic Animals

as Models of Human Diseases




Transfer of disease
-
causing human genes
creates transgenic organisms that are used to
study the development of human diseases and
the effects of drugs and other therapies as
methods of treating these disorders

HD Mice as Models



HD mice are extremely useful as models of
human neurodegenerative disorders


Used to study the progressive destruction of brain
structures in early disease stages


Used to link changes in brain structure with
changes in behavior


Used to screen drugs to improve symptoms or
reverse brain damage

Transferring Genes into Mammals





Microinjection of fertilized eggs



14.4 Testing for Genetic Disorders


Genetic testing



Used to determine if someone has a genotype for
a genetic disorder or is a carrier


Identifies individuals with a particular genotype



Genetic screening



Systematic search for individuals in a population
who have certain genotypes


Tests general populations that may have a low
frequency for a disorder


Four Types of Testing Programs



Newborn screening



Carrier testing



Prenatal testing



Presymptomatic (predictive) testing



Newborn Screening in the US



Newborn screening tests infants within 48 to 72
hours after birth for a variety of genetically
controlled metabolic disorders



All states require newborns to be tested


Most states screen for 3 to 8 disorders


New methods can scan for 30 to 50 disorders

Carrier and Prenatal Testing

Screen for Genetic Disorders



Carrier testing searches for heterozygotes that
may be at risk of producing a defective child


Done on family members or cultural groups with a
history of a genetic disorder such as sickle cell
anemia or cystic fibrosis



Prenatal testing tests a fetus for genetic
disorders (e.g. cystic fibrosis) or chromosome
abnormalities (e.g. Down syndrome)

Methods of Prenatal Testing




Amniocentesis can be done after the 15
th

week
of development



Chorionic villus sampling (CVS) is usually done
at 10 to 12 weeks of development


Prenatal Testing

Can Diagnose Sickle Cell Anemia



Recombinant DNA
-
based prenatal testing can
detect genetic disorders that cannot otherwise
be detected before birth



Sickle
-
cell beta globin genes have a distinctive
pattern of banding on a Southern blot


Normal gene: Two small fragments


Sickle gene: One large fragment

Prenatal Genetic Diagnosis (PGD)

Can Test Embryos for Genetic Disorders




Testing can be done on blastomeres from
in
vitro
fertilization, before embryo is implanted



Blastomere


Cell in early stages of embryonic development


Polar Body Biopsy





In a woman heterozygous for an X
-
linked
disorder, the X chromosome with the mutant
allele segregates into a polar body
or

an oocyte


Prenatal Testing

is Associated with Some Risks



Risks for mother and fetus


Infection, hemorrhage, fetal injury, and
spontaneous abortion



Risk of miscarriage


Amniocentesis: 0.5% to 1.0%


CVS: 1% to 3%

Cystic Fibrosis: Testing For 25 Mutations

in Different Ethnic Groups





With over 1,500 mutations identified, it is not
possible to test for all cases


Presymptomatic Testing

Can Be Done for Some Genetic Disorders




Presymptomatic testing (predictive testing)
identifies some individuals who will develop
adult
-
onset genetic disorders


Huntington disease


Polycystic kidney disease (PCKD)

Genetics in Society:

Who Owns a Genetic Test?



Families of children with Canavan disease, a
rare and fatal disorder, started a foundation to
obtain tissue samples and funding for research



The research hospital patented the gene and
charged participating families for the test



After a lawsuit, the hospital was allowed to
continue to license the test and collect royalties

Keep In Mind





Genetic disorders can be diagnosed using
biotechnology

14.5 DNA Microarrays in Genetic Testing



Testing for a wide range of genetic disorders is
possible using DNA chips (microarrays), which
can hold thousands of genes



DNA microarray



A series of short nucleotide sequences placed on
a solid support (such as glass) that have several
different uses

Uses of Microarray Technology



Detecting mutant genes


Individuals who will develop late
-
onset genetic
disorders such as polycystic kidney disease
(PCKD) and Huntington disease


Individuals at risk for disorders such as diabetes



Detecting differences in the pattern of gene
expression in normal and cancerous cells


Microarray Testing


Each field of the microarray contains a unique
sequence of single
-
stranded DNA



Test DNA and normal DNA are converted to
single strands, tagged with fluorescent dyes, and
hybridized to the chip



Each result has a different color


Normal alone is green; mutant alone is red


Both together are yellow; a blank field is black

Reading a Microarray Field





The tumor
-
suppressor gene
p53


14.6 DNA Profiles

as Tools for Identification




DNA profiles use variations in the length of short
repetitive DNA sequences to identify individuals
with a high degree of accuracy and reliability



This method is used in many areas, including
law enforcement, biohistory, conservation, and
the study of human populations

DNA Fingerprints



Minisatellites


Nucleotide sequences 14 to 100 base pairs long
organized into clusters of varying lengths; used in
the construction of DNA fingerprints



DNA fingerprint



Detection of variations in minisatellites used to
identify individuals


DNA Profiles


Short tandem repeats are now used routinely
instead of minisatellites, and
DNA profile

has
replaced the term
DNA fingerprint



Short tandem repeat (STR)



Short nucleotide sequences 2 to 9 base pairs
long organized into clusters of varying lengths



DNA profile


STR pattern used to identify individuals

DNA Profiles Can Be Made from

Short Tandem Repeats (STRs)



STRs range from 2 to 9 base pairs in length


CCTTCCCTTCCCTTCCCTTCCCTTCCCTTC
contains six repeats of the CCTTC sequence



Repeat numbers vary between individuals


A unique profile can be produced by analyzing
several STRs in a DNA sample


In the US, a standard set of 13 STRs (CODIS) is
used to prepare a profile

DNA Profiles Are Used in the Courtroom



Analysis of DNA profiles combines probability
theory, statistics, and population genetics to
estimate how frequently an allele combination is
found in a population



Population frequencies for STRs are multiplied
together to produce an estimate

Analyzing DNA Profiles





One suspect matches the crime scene evidence


Keep In Mind





DNA profiles are based on variations in the copy
number of DNA sequences

Other Uses for DNA Profiles





Two littermates, one a pure Shih Tzu, the other
a mixed breed



Genetic Journeys:
Death of a Czar





Forensics and several types of DNA evidence
were used to confirm that bones discovered in
1991 belonged to Czar Nicholas Romanov II, his
wife, and three of their five children




14.7 Social and Ethical

Questions about Biotechnology



Applications of recombinant DNA technology
have developed faster than societal consensus,
public policy, and laws governing its use



Efforts to inform legislators, members of the
legal and medical profession, and the public
often have lagged behind its commercial use


A balanced approach requires education and
debates on risks and benefits

Keep In Mind





The uses of biotechnology have produced
unresolved ethical issues