What is DNA?
In order to understand the science behind Jurassic Park ®, you
must understand a bit about DNA. What it is? What does it do? And
what it is made of? This section will provide the necessary
information for you.
- Deoxyribonucleic Acid (DNA)
- The basic structure of life made up of sugar, phosphate group and nitrogenous bases. It is the basic "blueprint" for life.
What does DNA look
like?
DNA basically
looks like a coiled zipper. It is made of two strands that are
connected and twisted together. The two strands run opposite of each
other. One strand runs 3' to 5' and the other runs 5' to 3'.
- DNA
is composed of 3 subunits.
- 1. Phosphate Group
2. Sugar (in this case the sugar is deoxyribose)
3. Nitrogenous base
- There are only 4 nitrogenous bases
- 1. Adenine (a)
2. Guanine (g)
3. Thymine (t)
4. Cytosine(c)
*Adenine and Guanine are purines, which means that they have
a 2-ring structure.
*Thymine and Cytosine are pyrimidines, which means that
they have a 1-ring structure.
*As in the case of all chemical substances, structure is related to function.
*DNA's
structure is in the form of a double helix. This means that it has
two strands (hence the word double) and that it's shape is coiled and
twisted.
*This structure allows DNA to replicate
itself and carry out its job (or function) as the code for life.
How does DNA replicate
itself?
- DNA replication is semi-conservative.
- DNA is read 3' to 5'.
- DNA builds itself 5' to 3'.
"Now our model for deoxyribonucleic acid is, in effect, a pair of
templates, each of which is complementary to the other. We imagine
that prior to duplication the hydrogen bonds are broken, and the two
chains unwind and separate. Each chain then acts templated for the
formation onto itself of a new companion chain, so that eventually we
shall have two pairs of chains, where we only had one before.
Moreover, the sequence of the pairs of bases will have been
duplicated exactly."
- Watson & Crick, 1953
In the above quote, Watson and Crick briefly explained the process of
DNA replication.
- The strand of DNA unwinds and
separates by an enzyme called DNA helicase.
- Now there are two separate strands, (the strands are
complementary to the other) each of the strands becomes a template.
- Free floating
nucleotides (in nucleus of the cell) pair up
with its complement on the template strand.
- Since DNA builds
itself from 5' to 3' and the two strands run oppositely, one strand
builds itself continuously. This strand is called the leading strand and it runs
from 5' to 3'. The other strand builds itself in fragments. This
strand is called the lagging
strand and it runs from 3' to 5'. The fragments are called Okazaki fragments.
- Then an enzyme called DNA polymerase, proofreads each new strand
and seals them up, thus creating two new completely identical DNA strands.
- The process continues and the DNA strand
replicates itself over and over again.
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