Frequently Asked Questions about Nucleic Acids

What is DNA and RNA? How are RNA and DNA used? Why are DNA and RNA studied?

What is a nucleic acid?

Nucleic acids are long, thread-like, molecule that are made up of chains of individual nucleotides that are found in all living animals, plants, bacteria and viruses. Most organisms use DNA to encode their genes, however some virus use RNA (HIV is one example). The nucleic acids were named because they were found in high concentrations in the cell nucleus.

What is DNA?

The full name of DNA is Deoxyribonucleic Acid. DNA is the main molecule used for storing the genetic code of an organism.

What is RNA?

The full name of RNA is Ribonucleic Acid.

What is the difference between DNA & RNA?

Chemically, a single hydroxide group on the ribose sugar group. RNA has a OH group at the 2' position of the ribose sugar while DNA has H at the same position. This minor chemical difference causes quite major changes to the chemical reactivity of molecules. In particular, it make RNA much more sensitive to hydrolysis (or another way of looking at it DNA is more resistant). RNA is easily damaged and must be treated with more care when studed in the lab (this is one reason if you are a scientist why working with DNA is better than working with RNA). DNA can be changed (transcribed) to RNA by various enzymes known as RNA polymerases. RNA can be converted to DNA by enzymes known as Reverse Transcriptases.

What do nucleic acids look like?

To the naked eye DNA and RNA are not very exciting - they generally look like a thick, colorless mucus with DNA being more "stringy" than RNA. At the atomic level the nucleic acids are much more interesting and have either single or double stranded structure (the famous double helix). DNA is most commonly double stranded composed from two single stranded nucleic acids joined together by hydrogen bonding. RNA is normally single stranded, however, many RNA molecules have double stranded region where the molecule has joined to itself.

Who discovered DNA?

The DNA was first isolated by Johann Friedrich Miescher in 1869. He named his new substance "nuclein" (which he had isolated from pus) as it was extracted from the cell nucleus. Nuclein was renamed by Richard Altmann to nucleic acid in 1889. Albrecht Kossel determined in 1893 that DNA is composed of four nucleic acid bases. Watson and Crick proposed a model for the structure of DNA in 1953. This work won them a Nobel prize (see below).

Didn't Watson & Crick discover DNA?

No. They proposed a model for the three dimensional structure of DNA in 1953. Because this structure was so elegant (although slightly wrong) and because it allowed a mechanism for gene replication, they were awarded, along with Maurice Wilkins, the 1962 Nobel Prize in Medicine for "their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material." Coincidently, both Crick and Wilkins were born in 1916 and died in 2004.

How is DNA studied?

There are lots of ways of studying DNA. First, it can be studied chemically, either in situ (inside the cell) or in vivo (literally in glass) after extraction away from the other materials found in the cell (like protein, lipids and carbohydrates). The different chemical groups found on the DNA and RNA subunits allow both nucleic acids to be selectively labeled using reactive chemicals that bind to the DNA or RNA. These chemicals allow the DNA to be visualized and or separated for analysis.

One of the most important ways DNA and RNA is studied is determining the order of nucleotide bases in a strand. This process is known as sequencing. For technical reasons DNA is most usually the molecule sequenced (RNA molecules are normally converted to DNA using a special enzyme known as a reverse transcriptase before being sequenced) and this is why the processes is most commonly known as DNA sequencing.

Where can I found out more about nucleic acids?

There are a number of sites that are excellent resources for those interested in nucleics acids. The first point to start would be Wikipedia (always a good place to start for most technical topics) another is MIT.

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