BIOL 200 Lecture Notes - Pseudoknot, Intron, Genomics
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Naveen Sooknanan McGill Fall 2011
Nucleic acids are active polymers located mainly I the nucleus of the cell, although some
important exceptions can apply (mRNA and tRNA in protein synthesis). These compounds were
discovered by the Swiss physician Friedrich Miescher in 1869.
This was done by isolating the nuclei of white blood cells found in pus from discarded
These compounds were found to be acidic, thus coined the term nucleic acids
Nucleic acids are crucial in protein synthesis as single stranded RNA and double stranded DNA
make up the first two steps of protein synthesis.
RNA, ribonucleic acids, are shorter and less stable than DNA and thus have a shorter life span
They are approximately 100s to 1000s of nucleotides in length
RNA can come in various shaped, including tRNA, mRNA and rRNA, which will be
DNA, deoxyribonucleic acid, is a double stranded double helix nucleic acid
Some DNA strands can be hundreds of millions of nucleotides in length
Both DNA and RNA are built from monomers called nucleotides. Although these nucleotides
differ slightly between RNA and DNA, they all contain backbone made from a pentose (5 carbon
sugar) and a phosphate group.
Ribose is the sugar found in RNA whereas 2-deoxyribose is
the sugar found in DNA
o In DNA, an OH on carbon 2 replaces the hydrogen
found in ribose
The pentose is covalently linked to a phosphate group which
provides the acidic quality of the nucleic acid
o This covalent bond is called a phosphodiester bond
The nucleotides also contain bases, of which there are 5: adenine, guanine,
uracil, thymine and cytosine. They can be further subdivided into 2
Adenine (A) and guanine (G) are purines and consist of two fused
Uracil (U, found in RNA), thymine (T, found in DNA) and cytosine (C) are pyrimidine
and have a single ring structure