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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?
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
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 15th 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 Mutationsin 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
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
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
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