Chapter 13Gene Technology

Section 1: Vocabulary PretestA. Strand of RNA labeled with a

radioactive element or fluorescent dye

B. Exact copy of a DNA fragment, a whole cell, or a complete organism

C. Enzyme that cuts DNAD. Small rings of DNA inside bacteria

cellsE. Pattern of DNA bands used for

identificationF. Process that separates DNA

fragments according to sizeG. DNA from two different sources is

combinedH. Technique that quickly produces

many copies of DNA fragmentsI. Small pieces of DNA needed to start

DNA replicationJ. Variations in the length of a DNA

molecule between known genesK. Repeating sequences of DNAL. Viruses or plasmids used to carry

DNA fragmentsM. Altering genetic material in order to

make new substances

1. Length Polymorphism2. Variable number tandem

repeats3. Polymerase chain reaction4. Primer5. Restriction enzyme6. Gel electrophoresis7. DNA fingerprint8. Genetic engineering9. Recombinant DNA10.Clone11.Vector12.Plasmid13.Probe

Section 1 Vocab Answer Key

1. Length Polymorphism J2. Variable number tandem repeats K3. Polymerase chain reaction H4. Primer I5. Restriction enzyme C6. Gel electrophoresis F7. DNA fingerprint E8. Genetic engineering M9. Recombinant DNA G10.Clone B11.Vector L12.Plasmid D13.Probe A

DNA Technology• DNA Technology is the

manipulation of DNA for practical purposes such as:o Identification using DNA

fingerprintingo Improving food cropso Identifying genetic diseases

before symptoms appearoResearch for cures or

treatments of genetic diseases

DNA Identification• About 0.1% of human DNA

differs from person to person. This variation allows us to:oIdentify peopleoDetermine paternityoIdentify human remainsoTracing human originsoProvide evidence in

criminal cases

Noncoding DNA• 98% of our DNA does not code for any

protein• It is called noncoding DNA• It contains many length polymorphisms

(variations in the length of the DNA molecule between known genes)

• It also contains short, repeating sequences known as variable number tandem repeats (VNTR)

• Geneticists use VNTR’s to determine how rare a particular DNA profile is.

Steps in DNA Identification

1. Isolate the DNA (make copies if needed)

2. Cut DNA into shorter fragments that contain known VNTR areas

3. Sort the DNA by size4. Compare the size

fragments in the unknown sample of DNA to those of known samples of DNA

Copying DNA: PCR• Polymerase Chain Reaction (PCR) is a technique that

quickly produces many copies of a DNA fragment (it is used if the DNA fragment is very small)

• Steps:o Start with a fragment of DNA with the sequence to

be copiedo Heat to denature and separate the DNA strandso Add primers (artificially made pieces of single-

stranded DNA that are complementary to the ends of the DNA fragment); DNA polymerase; and nucleotides

o Primers will bind to original strands; DNA polymerase will add free nucleotides to complete the strands

o Repeat about 30 times and generate millions of copies

Cutting DNA• Restriction Enzymes: bacterial enzymes that

recognize specific short DNA sequences and cut them.

• Cuts are usually asymmetrical and produce “sticky ends” so that other pieces of DNA with complementary sequences can bind to them.

Sorting DNA by Size• Gel Electrophoresis —technique that separates

nucleic acids or proteins according to their size and charge

• Steps:o Cut DNA with restriction enzymeso Place DNA into wells in a thick gelo Run electric current through the gelo Negatively charged DNA moves towards

positive end of the currento Smaller fragments move faster and farthero Transfer DNA to a nylon membrane and add

radioactive probeso Expose x-ray film to radiolabeled membrane to

produce a DNA fingerprint

Comparing DNA

• At least 13 VNTR loci comparisons are needed to make a positive DNA identification.

• Thirteen identical loci make the odds that two people will share a DNA profile about 1 in 100 billion

Recombinant DNA• Genetic engineering

—the process of altering the genetic material of cells or organisms to allow them to make new substances. It often involves recombinant DNA

• Recombinant DNA —DNA from one organisms is added to another

Pig expressing a jellyfish gene

Cloning Vectors• Clone —an exact copy of a

DNA segment, a whole cell, or a complete organism: or to make a genetic duplicate

• Vectors are used to clone DNA fragmentso They carry foreign DNA

from one organism to another

o They include bacteriophages and plasmids

Plasmids• Plasmids —small rings of DNA found

naturally in bacterial cells. They replicate separately from bacterial DNA

• Plasmids serve as excellent vectors for DNA

• Steps:o Isolate the plasmid from a

bacteria cell and the DNA of interest from a human cell (ex: gene coding for insulin)

o Used restriction enzymes to cut the DNA and the plasmid

o Mix the DNA and the plasmid together; sticky ends will bond

o Use DNA ligase to join them by forming permanent covalent bonds

o Transfer the recombinant plasmids back into bacterial cells

o Allow bacteria to reproduce (copying the plasmids to the new cells)

o Use probes to identify the colonies that have the desired gene. These bacterial cells will now be able to produce human insulin

Probes• A probe is a strand of

RNA or single-stranded DNA that is labeled with a radioactive element or fluorescent dye and that can base-pair to specific DNA, such as the donor gene in recombinant DNA.

• Probes will glow under UV light, allowing scientists to identify which recombinant colonies have the desired gene.

Medical Applications for DNA Technology

• Since 1982, more than 30 products made using DNA technology are now on the market.

• Examples:o Human insulino Proteins to treat immune system deficiencies

and anemiao Clotting factors for people with hemophiliao Human growth hormoneo Interferons for viral infections and cancero Growth factors for treating burns and ulcers

Section 2 Vocabulary Pretest

1. Human Genome Project

2. Proteome3. Single

nucleotide polymorphism

4. Bioinformatics5. Proteomics

A. An organism’s complete set of proteins

B. Combines biology, computer science and information technology

C. The study of all of an organism’s proteins

D. Unique spots in DNA where individuals differ by a single nucleotide

E. A research effort to sequence all of the human DNA code and locate within it all of the functionally important sequences (genes)

Answer Key1. Human Genome Project E2. Proteome A3. Single nucleotide polymorphism

D4. Bioinformatics B5. Proteomics C

The Human Genome Project

• The Human Genome Project began in 1990

• Its goal was to determine the sequence of all 3.3 billion nucleotides of the human genome and to map the location of every gene on each chromosome.

• More than 20 labs in 6 countries worked on the project

• It was completed in 2003

DARN

What Did We Learn?• Only 2% of our genome codes for proteins• Chromosomes have unequal distribution of

nucleotide sequences that are transcribe and translated

• Our genome is smaller than we thought; only about 30,000 -40,000 genes

• The same gene can encode different versions of a protein. An organism’s complete set of proteins is called its proteome.

• Transposons, pieces of DNA that move from one chromosome location to another make up half of our genome and play no role in development

• The are 8 million single nucleotide polymorphisms (SNP). These are spots where individuals differ by just one nucleotide.

Applications• We have

discovered the specific genes responsible for many diseases, which can help us to develop treatments and possibly cures for the more than 4,000 human genetic disorders

Section 3 Vocabulary Pretest

1. Gene therapy2. Nuclear transfer

cloning3. Telomere4. DNA vaccine5. Bioethics

A. Vaccine made from DNA of a pathogen but does not have disease-causing capabilities

B. A method for cloning entire organisms

C. The study of ethical issues related to DNA technology

D. Repeated sequences of DNA at the ends of chromosomes

E. A technique used to treat genetic disorders

Answer Key1. Gene therapy E2. Nuclear transfer cloning B3. Telomere D4. DNA vaccine A5. Bioethics C

Genetic Engineering: Medical

Applications• Gene Therapy —a technique used to treat a genetic

disorder by introducing a gene into a patient’s cells. It works best for disorders that result from the loss of a single protein. Ex: Cystic Fibrosis

• Cystic Fibrosis patients lack the CFTR gene: Result—excess mucus in lungs

• Steps of Gene Therapy:o Isolate the functional

gene from a healthy person

o Insert it into a viral vector

o Infect the patient with the recombinant virus (carrying the functional gene)

o The functional gene temporarily produces the missing protein, improving the symptoms of the disease

• Obstacles:o Cells that express the

highest levels of CFTR are deep in the lungs and are not being reached by the virus

o Surface cells die off regularly so the treatment must be repeated often

o Immune reactions to the treatment may occur

Genetic Engineering: Medical

Applications• Cloning —in 1996, the first

clone of an adult mammal was developed. It was a sheep named Dolly.o Dolly was created by a process known

as cloning by nuclear transfero Steps:

• Mammary cell with its nucleus was isolated from an adult female sheep

• Egg cell from another sheep was isolated and the nucleus removed

• The two cells were fused together and an embryo developed

• Embryo was transferred into a surrogate mother

• Dolly was born with nuclear DNA that was identical to the donor of the mammary cell

Professor Ian Wilmut and Dolly

Dolly suffered from premature aging and died at the age of 6. However, other clonedanimals have not experienced the same problem.

Why Clone Animals?• Most animal cloning is

done to alter the genome in some useful way.

• Examples:o Altered, cloned goats can secret

human blood clotting factors into their milk. This can then be extracted and used to treat hemophiliacs.

o Cloned pigs are altered so that their organs can be used in human transplants with a lessened risk of rejection.

o Altered, cloned mice are used in the study of many human diseases; like cystic fibrosis.

Genetic Engineering: Medical Applications

• Vaccines —DNA vaccines are now being researched. They are made from the DNA of the pathogen, except the disease-causing genes are removed.

• When injected into a patient, the patient will mount a defense and build up antibodies.

• If the real, disease-causing pathogen then enters the body; the antibodies will attack— preventing illness.

• DNA vaccines to prevent AIDS, malaria and certain cancers are currently being studied.

Genetic Engineering: Agricultural

Applications

• Genetically Modified (GM) Crops are becoming very common. Today, most crops can be genetically engineered to be:o More tolerant to

environmental conditions

o Resistant to weed killing herbicides

o Resistant to insects and other pests

o Resistant to diseaseso Improve nutritional

value

Ethical Issues• Bioethics —the study of ethical

issues related to DNA technology.

• Issues:o GM crops: are they healthy

for us and are they safe for the environment?

o Gene therapy: considered unethical if it involves reproductive cells that would affect future generations

o Cloning: considered unethical to clone human embryos for reproduction

o Genetic make-up of individuals should remain confidential to reduce the possibility of discrimination.