Genetics 101
Posted by Kristal Louie on Fri, Jan 22, 2010 @ 03:04 PM
Blog 1: It's in my DNA
We've heard from many of our study participants that spending some blog time on a "refresher" in genetics would be welcome. Some mothers in the SB Genetics Research Project have realized that much of what they once learned in Biology class has been long forgotten. To help jog your memory, we are starting a series of blogs simply called "Genetics 101" - not the most creative, but it get's the point across. Before I start, let me introduce myself. My name is Dennis Gilbert; I have a Ph.D. in Genetics from Johns Hopkins University and am one of the Principal Investigators for the SBGenetics Research Project.
Most simply, genetics is the science of heredity and variation. Studying genetics allows us to better understand the way in which similar characteristics among family members are maintained, and why differences between individuals occur. Geneticists examine a wide variety of inherited traits in a wide range of organisms, from fruit production in trees to metabolic diseases in humans. People who study genetics do so in a wide variety of situations, from research laboratories (like the SB Genetics Research Project) to pharmaceutical companies to crop fields. Being a geneticist nowadays is extremely exciting and rewarding as new breakthroughs that really make a difference in people's lives are consistently being made.
It's in my DNA! We've heard this expression a lot and probably have used it ourselves a few times. But, what is DNA?
DNA, or deoxyribonucleic acid, is a nucleic acid - a chemical compound that contains the genetic instructions for the development and functioning of all living organisms. The main role of DNA molecules is to ensure the long-term storage of our genetic information. DNA is often compared to a set of blueprints or a recipe, or a code, since it contains the instructions needed to construct other components of cells, such as RNA and protein molecules. DNA is found in almost every cell within the human body - from the white cells in your blood to the cheek cells in your mouth. Once the sequence of your DNA has been determined, as a combination of half the DNA of each of your parents, it does not change over your lifetime.
Chemically, DNA consists of two long chains of simple units called nucleotides, named for one of four types of molecules called bases. The four bases found in DNA are adenine (abbreviated A), cytosine (C), guanine (G) and thymine (T). It is the sequence, or order, of these four bases along the DNA chain that encodes your genetic information. There are approximately 3 billion bases in each of our cell that make up "my DNA". For illustrations and more details, the National Genome Research Institute has an excellent fact sheet.
Did you know? For many years after the discovery of DNA, most scientists remained convinced that proteins, not DNA, were the carriers of our genetic information. Why? It boiled down to the numbers. It was known that proteins were made of 20 different amino acids whereas DNA was made of only four different nucleotides. Thus, it makes some sense, then, that proteins could code for MUCH greater variety with their 20 amino acids than DNA could with its four nucleotide sequence. And the code for the complete set of instructions for human life would need enormous complexity and variety. As I'll discuss in a later blog, this great variety comes from how the code is read and then used by our body to transmit the genetic instructions. In 1952, Alfred Hershey and Martha Chase conducted what are now called the "blender experiments" to prove that DNA was indeed the genetic material and put the controversy finally to rest.
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