Biology ReviewDNA Technology

DNA is over 99.9 percent identical for any two

people of the same sex.

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Much of the text material is from, “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 also used and are noted.

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Outline

• Recombinant DNA • DNA fingerprinting• Genome project• Gene therapy• Safety, ethical, and moral concerns

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Recombinant DNA

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Recombinant DNA

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

• Research over a span of 30 years—often using E. coli bacteria—led to recombinant DNA technology.

• The technology can combine genes from different sources into the DNA molecule of a host cell.

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Definitions

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

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

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Transgenic Organism

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This glow-in-the-dark tobacco plant contains genes from a bioluminescent organism.

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Human Insulin

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

• Diabetes mellitus results if insufficient insulin is produced.

• A number of unhealthful outcomes can result from untreated diabetes.

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Bovine and Porcine Insulin

• Beginning in the 1920s, diabetes was treated using insulin from the pancreases of cows and pigs (bovine and porcine insulin).

• Allergic reactions sometimes resulted because the protein structures are not exactly the same as in human insulin.

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

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Synthetic Insulin

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

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

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

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

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Synthetic Insulin (continued)

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

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Genetically-Modified Foods

• Agricultural crops—including wheat and corn—have been selectively grown since antiquity to enhance their uses.

• DNA technology is replacing traditional growing programs to improve productivity.

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

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DNA Fingerprinting

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DNA Fingerprinting

• DNA technology has helped to revolutionize 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.

• This observation is particularly true of the non-coding, repetitive sec-tions of the nucleotide strands.

• DNA “fingerprinting” can determine to a high degree of certainty if the genetic material is from the same person or someone else.

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Applications

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

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

• The technique is being used in an increasing number of criminal and civil cases.

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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 also 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.

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DNA Fingerprinting Process

• The analysis of DNA “fingerprints” consists of several major steps:

1. DNA collection, including maintaining the chain of custody.

2. Amplifying (copying) the DNA to provide a sufficient sample for analysis.

3. Cutting the DNA into fragments and arranging them into a pattern.

4. Comparing the DNA markers or fragments from at least two differ-ent sources.

• The amplification process continues to be improved to allow the use of smaller DNA samples.

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DNA Matching

http://fig.cox.miami.edu

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Establishment of Paternity

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• 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.

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Human Genome Project

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Human Genome Project

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

• The human genome project by an international consortium of govern-ment-funded research groups is completed and much of the data has been published.

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

• Much of human DNA consists of non-coding, repetitive patterns of nucle-otides (A, C, G, and T).

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Repetitive Patterns

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• Segments of DNA containing thousands of base repetitions occur at the centromeres and the ends of chromosomes, possibly for structural sup-port.

• Other repetitive patterns of up to several hundred nucleotides are found between individual genes.

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

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Gene Therapy

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Gene Therapy

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

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

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Process

• The gene therapy 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 DNA virus.

• The virus is injected into the patient so that the gene can insert itself into the DNA.

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Process (continued)

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

• Bone marrow stem cells, which produce cells for the blood and immune system, are currently the best candidates for this type of gene therapy.

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Fetal Gene Therapyht

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The University of Southern California is a pioneer in fetal gene therapy—the

research is being conducted just a few miles from the ELAC campus.

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Safety, Ethical, and Moral Concerns

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Safety Concerns

• Concerns including that recombinant DNA technology could create deadly new microbes are being addressed by national governments.

• Laboratories must adhere to strict guidelines to ensure the microbes are not accidentally released.

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

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

• Potentially dangerous experiments have been restricted or banned.

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

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Ethical and Moral Concerns

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

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

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

• Other concerns have been raised too.

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Ethical and Moral Concerns (continued)

• 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.