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The Central Dogma of Life
In the process of studying the biochemical pathways
above it is important to remember the roles of the various players in the process
of life. These players are DNA, RNA & Proteins.
According to Vineet
Gupta, the information in most of organisms is transcribed from DNA, by
enzymes, to generate another class of molecules called Ribonucleic Acids (RNAs).
From there, it is translated to generate specific proteins. Proteins are the
molecules that carry out day-to-day chores for the cell. Thus, DNA is the carrier
of information, RNA the messenger and protein the executioner,
with a few exceptions. This is the Central Dogma of Life.
The Lego's of Life
DNA and RNA are made of four building blocks,
called bases or nucleotides.
The larger purines are Adenine (A) and Guanine
(G).
The smaller pyrimidines are Cytosine (C)
and Thymine (T)
For DNA the building blocks are: A, G, C
& T.
For RNA the building blocks are: A, G, C
& U.
RNA contains Uracil (U) instead of Thymine
(T)
In comparison proteins are composed of 20
major amino acids and some minor ones.
Sugar
Coated Plastic People
DNA is a polymer of nucleotide subunits,
each nucleotide comprising a sugar (deoxyribose), phosphate and one of
four different bases - the purines, adenine (A) and guanine (G) together
with the pyrimidines, thymine (T) and cytosine (C).
In the late forties it was discovered that:
Although the four DNA bases occur in varying
proportions in different organism
the number of A residues is always equal
to the number of T residues;
the number of G residues is always equal
to the number of C residues are present.
These quantitative relationships were important
clues to the three dimensional structure of DNA. They also give insight
on how genetic information is encoded in DNA and passed on from one generation
to the next.
Mnemonics
One can more easily remember the components
of DNA and RNA by the mnemonics, "CTAG" and "U after T". Here is
what C,T,A, G and U look like in both the unadorned and ribose sugar forms:
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Virtual
University Complete Biochemistry
L. Van Warren * (c) 1997-1998 Warren Design Vision * All Rights Reserved
t(more prevalent than cis relations except with Proline)