1

DNA is over 99.9 percent identical for any two people of the

same sex.

http

://w

ww

.live

from

thep

it.co

m

DNA TechnologyLecture 12, Part 2

2

Much of the text material in the lecture notes is from our textbook, “Essential Biology with Physiology” by Neil A. Campbell, Jane B.

Reece, and Eric J. Simon (2004 and 2008). I don’t claim authorship. Other sources were sometimes used, and are noted.

3

Outline

• Recombinant DNA • Human insulin• Genetically modified foods• DNA fingerprinting• Genomics• Gene therapy• Safety and ethical issues• Words and terms to know• Possible test items

4

Recombinant DNA

• In the 1940s, researchers demonstrated that the genes from individual bacteria could be combined in the laboratory without resorting to normal reproduction.

• Research over a span of 30 years, primarily using E. coli bacteria, led to the development of recombinant DNA technology.

• Genes from different sources are combined into the DNA molecule in a host cell.

5

Definitions

• A genetically-modified organism (GMO) is one that carries recombinant DNA.

• A transgenic organism is a GMO that carries DNA from different species.

6

Transgenic Organism

http

://w

ww

.cbs

.dtu

.dk

Glow-in-the-dark tobacco plant—contains genes from a bioluminescent organism.

7

Human Insulin

• Insulin is a protein produced by the pancreas to regulate the level of glucose in the blood.

• Diabetes (diabetes mellitus) results if insufficient insulin is produced.• A number of unhealthful outcomes can result from untreated diabetes.

http

://w

ww

.dva

.gov

.au

8

Bovine and Porcine Insulin

• Beginning in the 1920s, diabetes was treated using insulin from cows and pigs.

• Allergic reactions sometimes result since the protein structures are not exactly alike.

• By the 1970s, the supply of bovine and porcine insulin could not keep up with the demand.

Human insulin (to the left) and porcine insulin—the difference in the protein structure is just

one amino acid: alanine versus threonine.

http://www.bio.davidson.edu

Ala Thr

9

Synthetic Insulin

• Recombinant DNA technology enabled the mass production of synthetic insulin.

• Because the amino acid sequence for human insulin was already known, researchers could identify the DNA nucleotide sequence that would code for the protein.

• Individual segments of DNA were synthesized and linked to form insulin genes.

• The artificially-produced human genes were inserted into E. coli bacteria that could rapidly multiply and produce large quantities of insulin protein.

10

Reliance on Synthetic Insulin

http://www.diabeticmommy.com

Today, more than four million people in the United States rely on synthetic insulin.

11

Genetically-Modified Foods

• Since antiquity, agricultural crops have been selectively bred to enhance their use.

• DNA technology is replacing traditional breeding programs to improve farm productivity.

• Some corn varieties, for example, have been genetically modified to resist the European corn borer.

12

Cornfield

http://www.precisiongps.com

Corn is a major economic crop, with a variety of uses including for food products, high fructose corn syrup,

animal feed, and ethanol.

13

European Corn Borer

http://ipm.uiuc.edu

http://ipm.uiuc.edu

The insect was first found in the northeastern United States in 1917. It has spread to the South, Midwest,

and High Plains regions.

14

Strawberries and Rice

• Some strawberry varieties have been genetically modified to resist cold weather.

• Transgenic rice varieties have been developed as a source of iron and beta carotene for vitamin A production.

Transgenic ‘golden rice’ to the right

http

://w

ww

.agb

iofo

rum

.org

15

DNA Fingerprinting

• DNA technology has revolutionized forensics, the scientific analysis of evidence in crime scene and other legal investigations.

• The DNA sequence of every person is unique except in monozygotic (identical) twins.

• DNA fingerprinting can determine if genetic material is from the same person or different people.

16

Applications

• DNA fingerprinting has become a standard method for law enforcement and legal proceedings since its introduction in 1986.

• DNA can be obtained from body sources including blood, tissues, hair, bone, saliva, and semen.

• The technique has been used in a number of high-profile legal and civil cases.

17

More Recent Applications

• DNA technology continues to be used in identifying small fragments of human remains from the terror attacks of September 11, 2001.

• DNA has been used to exonerate prisoners who were innocent of the charged crimes.

http://dna.view.com

From the website of an appeals attorney specializing in DNA

evidence.

18

DNA Fingerprinting Process

• The analysis of DNA ‘fingerprints’ has several major steps:

1. DNA collection, including maintaining the chain of custody2. Amplifying (copying) the DNA to provide a sufficient sample 3. Cutting the DNA into fragments and arranging them into a pattern4. Comparing the DNA markers or fragments from different sources

• The amplification process has been improved to enable the use of much smaller DNA samples.

19

DNA Matching

http://fig.cox.miami.edu

20

Establishment of Paternity

http

://w

ww

.fox

new

s.co

m

• In cases involving the establishment of paternity, blood typing can rule-out some possibilities, but it cannot conclusively determine who is the father of conception.

• Comparing DNA samples from the mother, child, and purported father can definitively establish paternity.

• Recently, it was shown that Thomas Jefferson (the third U.S. President) or a close relative fathered at least one of the children of his slave, Sally Hemings.

21

Genomics

• Genomics, the science of studying genomes, was established in the past 20-25 years.

• The initial focus was on pathogenic bacteria, which cause pneumonia and meningitis.

• H. influenzae (not the flu virus) contains about 1.8 million nucleotides and 1,709 genes.

Genome = an organism’s complete set of genes.

22

Expanding Research

• More complex organisms, with much larger genomes, were subsequently studied for their DNA sequences.

• By 2003, the genomes of more than 100 organisms had been sequenced.• Researchers completed the sequencing of the human genome within the

past few years.

23

Journal Covers

http://biology.iupui.eduhttp://genome.imim.eshttp://www.molgenmpg.de http://www.bioinfo.mbb.yale.edu

The progression of complexity in genome research is shown on scientific journal covers—sea urchin, mosquito, mouse,

and human.

24

Human Genome Project

• The human genome has about 3.2 billion nucleotide pairs and 25,000 to 35,000 genes.

• The Human Genome project, undertaken by an international consortium of government-funded research groups, is completed and has published much of its data.

25

Why It’s Important

The understanding of the human genome sequence opens many possibilities for medical diagnoses and treatments.

http

://g

enom

e.im

im.e

s

26

Challenges

• An understanding of the human genome is a challenge due to its large size, and because only relatively small segments of DNA code for mRNA and tRNA.

• Much of human DNA consists of repetitive patterns of the nucleotides (A, C, G, T).

27

Repetitive Patterns

htt

p://

ge

nom

e.w

ellc

ome

.ac.

ak

• Segments of DNA containing thousands of base repetitions occur at the centromeres and ends of chromosomes, possibly providing structural support.

• Other repetitive patterns, consisting of several hundred nucleotides, are found between individual genes.

• The markers often used in DNA fingerprinting are the repetitive patterns since they are unique to the individual.

28

Gene Therapy

• Human gene therapy uses recombinant DNA to treat some types of disorders and diseases.

• Gene therapy might be used to correct a genetic disorder—possibly permanently, or in other instances just long enough to treat a medical problem.

29

Process

• The process involves taking a normal gene from a donor, and isolating and cloning it using recombinant DNA technology.

• The gene of the recombinant DNA is inserted into a vector—usually a non-harmful virus.

• The virus is injected into the patient—the gene the inserts itself into the DNA.

• The newly-introduced gene is transcribed and translated to produce the desired protein.

• Bone marrow stem cells—that produce cells for the blood and immune system—are good candidates for gene therapy.

30

Fetal Gene Therapyht

tp:/

/ww

w.e

m1.

mol

med

.uni

-erla

ngen

.de

The University of Southern California is a pioneer in gene therapy—the research is conducted a few miles

from the ELAC campus.

31

Safety

• Early concerns, included that recombinant DNA technology could create deadly new microbes, are being addressed by national governments.

• Laboratories must adhere to strict guidelines to prevent microbes from being accidentally released.

• They must adhere to strict procedures to prevent worker contamination and infection.

• The microbes are genetically-crippled so that cannot reproduce and survive outside the laboratory.

• Potentially dangerous experiments have been banned.

Science fiction film from the early-1970shttp://thisdistractedglobe.com

32

Food Concerns

• Genetically-modified strains are a sizeable portion of some agricultural crops, including wheat and corn.

• Crops have been genetically-engineered for higher yield, and resistance to insects, viral diseases, and drought.

• Some people fear genetically-modified plants could be harmful to human health or the environment.

• Another concern is that genetically-modified crops might pass their genes to similar species in nearby wild areas or to adjacent farms that rely on natural growing methods.

33

Controversy

• The European Union suspended the introduction of new GM crops, and is considering the banning of GM foods.

• The U.S. National Academy of Sciences issued a report that genetically-modified crops do not pose any health or environmental risks.

• The debate is unlikely to subside any time soon due to a clash of world views.

34

Ethical and Moral Issues

• DNA technology raises legal, ethical, and moral questions—often with few clear answers.

• Should genetic engineering of gametes and zygotes be permitted to breed for desirable physical characteristics in human children?

• Should we allow genetic changes that could be beneficial today, but possibly detrimental to the long-term health and survival of a species?

35

More Ethical and Moral Issues

• Should we record the DNA fingerprint of every person, possibly as early as birth?

• Should employers and insurance companies be allowed to screen job applicants for potentially harmful genes?

• Should we take on a creator role for producing offspring including humans?

• The list of questions is long—the issues need debate and careful deliberation by society.

36

Words and Terms to Know

• DNA fingerprinting• E. coli bacteria• Fetal gene therapy• Gene therapy• Genetically-modified food• Genetically-modified organism

• Genomics• Human genome• Marker• Recombinant DNA• Transgenic organism

37

Possible Test Items

5. Describe how synthetic insulin is synthesized using recombinant DNA technology.

6. Describe gene therapy, and how knowledge of viruses and the trans-cription and translation processes are applied.