Highlight HEALTH

As 2007 comes to a close, I would like to thank you for your readership. Just over one year ago, I launched two websites, Highlight HEALTH and the Highlight HEALTH Web Directory. Here at Highlight HEALTH, my goal was to write about biomedical research I found interesting and to make it easier for people to understand research findings, empowering them to have more productive discussions with their physicians and to make informed decisions about healthcare. The Highlight HEALTH Web Directory is my endeavor to catalog and make available health-related websites I find to be informative and useful. More recently, I’ve also started writing about Web 2.0 in Health, Fitness and Medicine, and plan to publish a series of review articles on a number of health-focused social networks.

This past month, I started the Highlight HEALTH Network, an aggregation of content from both sites to allow readers to keep up with the latest articles on Highlight HEALTH and the newest additions to the Highlight HEALTH Web Directory, all from a single source.

Here are the most popular articles for 2007 (top 20 based on the number of page views/number of days posted):

1. The Highlight HEALTH Network RSS Dashboard Widget
2. Smoking Cessation Timeline: What Happens When You Quit
3. Dichloroacetate Not Ready for Therapeutic Use
4. The Highlight HEALTH Network
5. New Common Cold Virus Variant Deadly
6. Common Therapy for Prostate Cancer May Promote Metastasis
7. Overweight Kids and TV: An Advertising Epidemic
8. Saline Nasal Irrigation More Effective than Spray for Chronic Sinus Symptoms
9. Pediatric Grand Rounds 2.8
10. The Genetics of Panic Disorder
11. Smoking Duration vs. Intensity and the Impact on Lung Cancer Risk
12. Social Networks and Health - The Research and the Reviews
13. Quercetin
14. American Obesity Rate Levels Off
15. Biodegradable Polymers for Drug and Gene Delivery
16. Individual Genetics, Coffee Consumption, BRCA1 and Breast Cancer
17. The Flu, Your Health and the Importance of Vaccination
18. SCHIP Funding and Fiscal Irresponsibility
19. DNA Amplification by Polymerase Chain Reaction (PCR)
20. Sinus Congestion

Thank you and Best of Health in the coming year!

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Just in time for the holidays, Highlight HEALTH and the Highlight HEALTH Web Directory now offer an aggregated news feed.

The Highlight HEALTH Network is currently an aggregation of content from two news feeds:

• Highlight HEALTH
• The Highlight HEALTH Web Directory: New Additions

The aggregation of both feeds allows readers to easily keep up with the latest articles on Highlight HEALTH and the newest additions to the Highlight HEALTH Web Directory. You can subscribe to the Highlight HEALTH Network via RSS or email.

Do you currently subscribe to feeds on either Highlight HEALTH or the Highlight HEALTH Web Directory? Not to worry … these single feeds will continue uninterrupted. However, by subscribing to the Highlight HEALTH Network, you can stay up-to-date with new articles and websites, all from a single source.

Here’s some highlights of recent articles on Highlight HEALTH:

Here’s some highlights of recent additions to the Highlight HEALTH Web Directory. Hint: click on the category title to see all the websites currently listed.

Next up: plans to add a third feed to the Highlight HEALTH Network, which will include articles and reviews on Web 2.0 in Health, Fitness and Medicine from the Highlight HEALTH Web Directory.

Happy Holidays!

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What does the diagnosis of hereditary diseases, the detection and diagnosis of infectious diseases, personalized DNA sequencing, DNA cloning, genetic functional analysis, genetic fingerprinting and DNA-based phylogeny have in common?

The all employ a widely used molecular technique called polymerase chain reaction or PCR.

The idea was conceived by Kary Mullis in the early 1980s and was first described, albeit briefly, in an article investigating the mutation that causes sickle cell anemia [1]. The details of the method and its uses were discussed in greater detail over the next two years [2-3]. PCR revolutionized molecular genetics by allowing rapid duplication and analysis of DNA.

The PCR method

PCR is used to amplify a specific region of DNA in order to produce a large number of nearly identical copies. The method uses a heatstable DNA replication enzyme called a DNA polymerase, the four deoxynucleotide building blocks of DNA and two small single-stranded DNA segments called primers, which flank the “target” region of DNA to be amplified and are complementary to each strand (meaning the matching strand to which its bases pair).

There are 3 basic steps in PCR that are carried out at different temperatures to create conditions optimal for:

1. DNA denaturation (meaning to separate the double-stranded DNA into single strands).
2. Primer binding or hybridization to each of the single strands of DNA at either the beginning or the end of the target sequence, depending upon the single-strand of DNA. Hybridization combines complementary, single-stranded DNA into a single molecule. This process is called annealing.
3. DNA polymerase elongation. The enzyme attaches to the primer-single-stranded DNA duplex and synthesizes the complementary strand of DNA, using the existing single-strand as a template.

Newly synthesized DNA strands can serve as additional template for complementary strand synthesis. PCR rapidly amplifies DNA; because both strands are copied, there is an exponential increase in the number of copies. Assuming there is only a single copy of the target gene before cycling starts:

After 35 cycles of PCR, there will be over 68 billion copies! In reality, PCR starts with many copies of the target gene, so the end result is typically higher. Each cycle only takes a few minutes. Factoring in the time to change temperatures, the entire process can be done in several hours.

More recently, a new method of PCR quantification called real-time PCR or quantitative real-time PCR (qRT-PCR) was developed [4]. qRT-PCR enables the detection and quantification of a specific DNA sequence using a fluorescent reporter (either a dye or a modified DNA oligonucleotide probe), which increases in direct proportion to the amount of DNA amplified in a reaction.

It’s easier to understand how PCR works with pictures. Visit DNA Interactive to view an animation of PCR. DNA Interactive is an award-winning educational web site created in 2003 to celebrate the 50th anniversary of the discovery of the DNA double helix structure.

The advent of PCR and recombinant DNA technologies have enabled numerous applications in basic and clinical research. PCR is often regarded as one of the most important scientific advances in molecular biology. Indeed, Kary Mullis holds the only Nobel Prize ever awarded to a scientist in the biotechnology industry. He received the Nobel Prize for Chemistry in 1993.

References

1. Saiki et al. Enzymatic amplification of beta-globin genomic sequences and restriction site analysis for diagnosis of sickle cell anemia. Science. 1985 Dec 20;230(4732):1350-4.
   View abstract
2. Mullis et al. Specific enzymatic amplification of DNA in vitro: the polymerase chain reaction. Cold Spring Harb Symp Quant Biol. 1986;51 Pt 1:263-73.
   View abstract
3. Mullis and Faloona. Specific synthesis of DNA in vitro via a polymerase-catalyzed chain reaction. Methods Enzymol. 1987;155:335-50.
   View abstract
4. Higuchi et al. Kinetic PCR analysis: real-time monitoring of DNA amplification reactions. Biotechnology (N Y). 1993 Sep;11(9):1026-30.
   View abstract

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