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Stem Cells: The Revolution in Cell Technology
The issue of stem cells has recently burst upon the public awareness. This short enhancement chapter introduces you to this revolutionary cell technology, which promises to open a whole new field of regenerative medicine but is highly controversial.

DNA Fingerprinting: You Be the Judge
In this interactive exercise, you analyze the DNA evidence presented in real courtroom trials, attempting to ascertain the guilt or innocence of the suspect in each instance. The DNA samples from the victim, perpetrator, and suspect are presented from a library of real cases, and you choose the DNA probes to use and then compare the evidence.

Genetic Engineering. The ability to move specific genes from one organism to another is revolutionizing biology. But while the potential to improve the human condition is riveting the scientific community, many people are scared that genetic engineers are altering nature with consequences we can neither predict nor control. Much of the controversy has centered on gene-modified foods.

1. How genetic engineering is done.
2. The real promise of genetic engineering.
3. Finding useful genes: Cassava's relatives.
4. Measuring the risks of bioengineering.
5. Should we label genetically modified crops?
6. Gene engineers should renounce the terminator.
7. Frankenstein grass is poised to invade our yards.

How Genetic Engineering Is Done
All of genetic engineering relies on the surprising discovery of enzymes that make offset cuts in double-stranded DNA — one strand is cut several bases from the other. This creates complementary single-stranded "tails" on the fragments, so that any two genes excised by the same enzyme can be stuck together! The revolution in genetic engineering that is changing modern biology all derives from this one surprising discovery.

Assessing the Risks of GM Foods
There has been considerable public discussion about the potential risks of genetically modified crops, so-called GM foods. The intense feelings generated by this dispute point to the need to understand how we measure the risks associated with gene manipulation of plants. Two sorts of risks need to be considered. First, is eating genetically modified food dangerous? Second, are GM crops potentially harmful to the environment? On both questions, there is profound public distrust on the one hand, and practically universal scientific consensus that GM crops are safe, on the other.

Trading Hormones Among Fishes: Gene Technology Lets Us Watch What Happens
The polymerase chain reaction (PCR) is a technique that allows a researcher to quickly and easily generate many copies of a segment of DNA. Prior to the development of this procedure, researchers had amplified DNA sequences by the laborious procedure of inserting them into bacterial DNA, growing large cultures of the sequence-carrying cells, and then harvesting the desired DNA. The PCR method is both faster and far easier.

Researchers are now expanding the uses of PCR beyond the simple amplification of DNA. Hamid Habibi, Maurice Moloney, and colleagues at the University of Calgary have developed a new laboratory method that uses PCR to quantify the relative levels of DNA in a sample, a method they call Quantitative PCR (Q-PCR). The group had set out to isolate an insulin-like growth factor (IGF-I) from goldfish liver, following a treatment with growth hormone or gonadotropin-releasing hormone. The researchers developed their competitive quantitative PCR technique to provide a highly accurate way of measuring IGF-I mRNA levels in treated goldfish livers.