28 Zero to Genetic Engineering Hero - Chapter 1 - Isolating DNA, the Blueprints of Life
small, such as oxygen gas (O
) with only two atoms, to
O) with three atoms, to DNA which is by far
the most enormous at millions or billions of atoms. In
the DNA extraction exercise, you saw with your own
eyes how much DNA was in the strawberry cells - that
glob of DNA was made of trillions of atoms. And the
other macromolecules, such as the proteins, lipids,
and carbohydrates bound up by the surfactants into
micelles, were made up of trillions more.
DNA: The blueprints of living cells
A blueprint is used for storing information about the
construction and maintenance of a factory and the
Blueprints for the building may have information
about the structural components (e.g. brick outer shell
supported by iron beams), the ventilation systems (e.g.
made of aluminum ducting), the complex electrical
e.g. different voltages, wires, and loca-
tion of the outlets). Blueprints can also determine how
a building is built. Is a crane needed? If so, scaffolding
may be erected to accommodate for this.
inside, how it is positioned, and the speed at which it
operates. A lot of equipment and infrastructure is
permanently connected to the factory. In this case,
the components, machines and the factory building
itself meld to become one. In other words, a factory is
not just a building, but is the building, equipment,
and even the people inside, turning raw materials
into end products.
Why are we talking about factories? Factories as we
know them are analogous to living cells—except they
are much larger and made of different materials. The
factory are comparable to the blueprints of living
cells. In the case of living cells, however, there is not
a miniature piece of blue paper rolled up in every cell.
There is a microscopic chemical string, the DNA.
Unlike a factory blueprint that you can see with your
eyes, hold in your hands, and is written in a language
that is well understood, the blueprint of a living cell,
DNA, is a microscopic “chemical string” of nucleotide
building blocks. This string has a distinct “language”
that all living cells know how to read and write. Only
lind Franklin, and Maurice Wilkins discovered the
structure of DNA have we begun to understand it and
its language. Here is some of what we know:
DNA is made of four chemical building blocks called
nucleotides that are attached to one another in vari-
ous orders to form a “string” of the nucleotides that
can be thousands to millions of nucleotides long.
Each nucleotide is made of CHOPN, and each nucleo-
tide is made up of three “sub-molecules” called a
phosphate, a nitrogenous base, and a deoxyribose
sugar (Figure 1-16). Have a look at Figure 1-16, do you
see the CHOPN chemical elements?
Phosphate is a molecule with a phosphorus atom
bound to four oxygen atoms. Phosphate is a critical
component of the “sugar-phosphate” backbone of
DNA (Figure 1-17). The phosphate group is very
negatively charged and is what gives DNA an overall
negative charge. As you saw in Chapter 1’s exercise,
the negative charge of DNA is an important chemi-
cal characteristic that you took advantage of to
extract DNA from cells using chemistry.
Nitrogenous bases are the variable part of a nucle-
otide. While every nucleotide has the same
backbone, there are four different nitrogenous
bases in DNA - Guanine, Thymine, Adenine, and
nitrogenous bases? If you have trouble, try the What
is DNA? application mentioned in the hands-on
exercise. The nitrogenous base is the part of the
nucleotide molecules that is the information that
the cell machinery “reads”.
Deoxyribose is a sugar ring that is the “D” in DNA.
Deoxyribose connects to both the nitrogenous base
and the phosphate (Figure 1-16). When multiple
nucleotides are connected, as seen in Figure 1-16,
you’ll see that the deoxyribose also connects to the
phosphate of the next nucleotide. The deoxyribose
and the phosphate together form the “sugar-phos-
phate” backbone of DNA (Figure 1-17).
Figure 1-15. Comparing factory blueprints (left) to the blue-
prints of a living cell, DNA (right).
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