Figure 3.1: The central dogma of molecular
biology
Proteins serve structural and functional roles that give
individual
cells, and by extension whole organisms, specific structures and
functional characteristics.
When many people think of proteins, they think of foods such as meat
and beans. While animal muscle and plant seeds are commonly known as
excellent sources of
dietary protein, proteins are also present in many other parts of
animals and plants. Proteins perform functional and structural roles.
Examples of proteins include keratin, which makes skin waterproof,
and myosin, which interacts with other proteins in muscles to make
them flex.
DNA contains information that describes the construction of
proteins.
The process of protein synthesis is as follows:
- DNA contains the information to produce proteins.
- Information encoded in DNA is transcribed into a molecule called
messenger RNA (mRNA); effectively a 'working copy' of the DNA
sequence of a given gene.
- mRNA is translated into protein by the protein synthesis
machinery,
the composition of the resulting protein corresponding to the
original DNA instructions.
This basic mechanism is conserved in all life forms, from
bacteria to
humans. The implication of this common process that converts
information
in DNA into functional proteins is that similar techniques can be
used to investigate and manipulate all biological systems.
Furthermore, it is possible
to make therapeutic proteins for humans, for example, in organisms as
distantly related as bacteria.
While there are some exceptions (e.g. retroviruses and prions) to
the order and direction of information flow described by the central
dogma, these examples still fit within the framework of the central
dogma. Understanding
the roles of DNA, RNA, and protein and their relationships to each
other is essential to understanding molecular biology.
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