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Friday, June 26, 2009

DNA on the Witness

Eric S. Lander, D. Phil.
Director, Center for Genome Research
Massachusetts Institute of Technology


What I would like to talk about today is the use of DNA in identification. I think it does a marvelous job of illustrating the unexpected consequences of discoveries in basic science.

There is a tremendous diversity amongst human beings. What a marvelous range there exists of human diversity, in height, in weight, in skin color, in faces. It's what makes life wonderful, what makes the human species so wonderful. And it makes us wonder what underlies this tremendous diversity in physical appearance. We know, in fact, that in large measure, physical appearance is genetically determined. We know this by looking at identical twins. When you look at identical twins it's not hard to see striking similarity between them. You do indeed see difference, but the similarity is really much more striking. And this tells us that identical DNA tends to produce identical physical appearance.

Agricultural Biotechnology: Breeding Program


Foundation Seed

The basis of any plant breeding program is its germplasm, represented by breeder's or foundation seed. A limited inventory of foundation seed is maintained. These seed inventories are usually kept in more than one storage location and should be in secure storage facilities with controlled temperature and humidity. The controlled storage is tmaintains seed quality,helping insure viability and seedling vigor. Maintaining this inventory is one of the keys to a successful breeding program. Careful generation of foundation seed is an on going part of the breeding program. Watermelon seeds, if properly cleaned and dried and prepared for storage can keep for several years. Part of the administrative portion of the program is managing the foundation seed inventory.

Introduction to Nucleic Acids and Application to Infectious Disease Detection

Introduction

Advances in technology in the last 30 years have driven changes and advancements in how the hospital clinical or medical laboratory analyzes specimens to provide useful data to physicians for patient diagnosis, monitoring or treatment of disease states or disorders.  Prior to the 1970’s most tests that a physician ordered on his or her patients were analyzed in the hospital clinical laboratory using manual methods – which involved careful pipetting of reagents and patient samples, mixing in test tubes and using a spectrophotometer to measure; performing blood cell counts using a specially designed slide (hemacytometer) and microscope; or streaking specimens for culture growth and performing a number of biochemical tests manually on the organism to determine its identity. 

In the 1970’s automated testing for analysis of blood samples (e.g. glucose, cholesterol) was introduced that allowed the clinical laboratorian to perform more tests more quickly.  In the 1980’s enzyme immunoassay allowed the introduction of more efficient testing methods for hormones, drugs of abuse, and therapeutic drug monitoring. 

In the late 1980’s and 1990’s further miniaturization of electronics brought the advance of “Point of Care” technology that increased testing at the patient’s bedside or in the physician’s office.  The advancing technology of today is DNA or Molecular Technology.  Molecular technology is at the threshold of many possibilities for use in the clinical or hospital laboratory.  Currently, molecular technology is used to identify disease causing organisms, genetic disorders or tumors. 

The purpose of this learning unit is to introduce the basics of nucleic acids so that current molecular technologies can be understood.  Here are the learning goals for this unit:

  • Explain the components and basic structure of DNA & RNA
  • Discuss the roles of DNA & RNA’s in protein synthesis
  • Discuss the principle of the hybridization probe assay

First you will learn about DNA & RNA and their role in the cell.  Then one principle of a molecular test will be presented to illustrate how this new technology is used to identify some infectious organisms. 

Where Did Biotechnology Begin?

With the Basics

Certain practices that we would now classify as applications of biotechnology have been in use since man's earliest days. Nearly 10,000 years ago, our ancestors were producing wine, beer, and bread by using fermentation, a natural process in which the biological activity of one-celled organisms plays a critical role.

In fermentation, microorganisms such as bacteria, yeasts, and molds are mixed with ingredients that provide them with food. As they digest this food, the organisms produce two critical by-products, carbon dioxide gas and alcohol.

In beer making, yeast cells break down starch and sugar (present in cereal grains) to form alcohol; the froth, or head, of the beer results from the carbon dioxide gas that the cells produce. In simple terms, the living cells rearrange chemical elements to form new products that they need to live and reproduce. By happy coincidence, in the process of doing so they help make a popular beverage.

Bread baking is also dependent on the action of yeast cells. The bread dough contains nutrients that these cells digest for their own sustenance. The digestion process generates alcohol (which contributes to that wonderful aroma of baking bread) and carbon dioxide gas (which makes the dough rise and forms the honeycomb texture of the baked loaf).

Discovery of the fermentation process allowed early peoples to produce foods by allowing live organisms to act on other ingredients. But our ancestors also found that, by manipulating the conditions under which the fermentation took place, they could improve both the quality and the yield of the ingredients themselves.

Crop Improvement

Although plant science is a relatively modern discipline, its fundamental techniques have been applied throughout human history. When early man went through the crucial transition from nomadic hunter to settled farmer, cultivated crops became vital for survival. These primitive farmers, although ignorant of the natural principles at work, found that they could increase the yield and improve the taste of crops by selecting seeds from particularly desirable plants.

Farmers long ago noted that they could improve each succeeding year's harvest by using seed from only the best plants of the current crop. Plants that, for example, gave the highest yield, stayed the healthiest during periods of drought or disease, or were easiest to harvest tended to produce future generations with these same characteristics. Through several years of careful seed selection, farmers could maintain and strengthen such desirable traits.

The possibilities for improving plants expanded as a result of Gregor Mendel's investigations in the mid-1860s of hereditary traits in peas. Once the genetic basis of heredity was understood, the benefits of cross-breeding, or hybridization, became apparent: plants with different desirable traits could be used to cultivate a later generation that combined these characteristics.

An understanding of the scientific principles behind fermentation and crop improvement practices has come only in the last hundred years. But the early, crude techniques, even without the benefit of sophisticated laboratories and automated equipment, were a true practice of biotechnology guiding natural processes to improve man's physical and economic well-being.

Harnessing Microbes for Health

Every student of chemistry knows the shape of a Buchner funnel, but they may be unaware that the distinguished German scientist it was named after made the vital discovery (in 1897) that enzymes extracted from yeast are effective in converting sugar into alcohol. Major outbreaks of disease in overcrowded industrial cities led eventually to the introduction, in the early years of the present century, of large-scale sewage purification systems based on microbial activity. By this time it had proved possible to generate certain key industrial chemicals (glycerol, acetone, and butanol) using bacteria.

Another major beneficial legacy of early 20th century biotechnology was the discovery by Alexander Fleming (in 1928) of penicillin, an antibiotic derived from the mold Penicillium. Large-scale production of penicillin was achieved in the 1940s. However, the revolution in understanding the chemical basis of cell function that stemmed from the post-war emergence of molecular biology was still to come. It was this exciting phase of bioscience that led to the recent explosive development of biotechnology.