Personalized Medicine - Translational Informatics: Realizing the Promise of Knowledge-Driven Healthcare - page 33

Fig. 3.1 DNA takes the form
of a double helix, with
nucleotide pairs as the
“rungs.” Adenine pairs with
Thymine, and Guanine pairs
with Cytosine (Reprinted
with permission from:
OpenStax College. Organic
Compounds Essential to
Human Functioning,
OpenStax_CNX Web site.
http://cnx.org/content/
m46008/1.4/ , Jun 27, 2013)

Nitrogenous bases:

Adenine

Thymine

Guanine
Cytosine

Base pair

Sugar phosphate backbone

When a given gene is activated or “expressed”, the information from that portion
of the DNA is transferred to a complementary strand of ribonucleic acid , or RNA,
through a process known as transcription . RNA is made up of nucleotides similar to
those in DNA, but with uracil (U) instead of thymine (T). G still pairs with C, and
A with U. This complementary strand of RNA undergoes certain processing (e.g.
splicing out of introns, addition of a “poly-A tail”, etc.) and is then translated into a
polypeptide sequence, or chain of amino acids. The polypeptide then folds in three
dimensions and may undergo post - translational modifi cations , e.g. additions of
functional molecular groups, resulting in a functional protein molecule. Ultimately,
proteins are broken down into amino acids and derivative compounds (metabolites)
and eliminated from the cell. Figure 3.2 summarizes this process. The term genom-
ics may be used to refer to data regarding DNA sequence or gene expression (A, B).
The term transcriptomics refers to gene expression (B). Proteomics may be used to
refer to all aspects of proteins, from sequence to shape to modifi cations (C, D). And
metabolomics is used to refer to metabolites, the smaller molecules that are gener-
ated as a result of the breakdown of proteins (E).