270 MHR • Unit 3 Molecular Genetics
Biology At Work
Molecular Biologist
Alison Morrison is a molecular biologist with a mining
company in Trail, British Columbia. When she thinks
of mining, she considers an image of something best
viewed through a microscope — bacteria. Surprising
as her focus may seem, certain bacteria can be used
to help recover metals.Alison MorrisonNew Technologies
The unique metabolisms of these bacteria are leading to
the development of new mining technologies. Known as
bio-leaching or bio-oxidation (see “bioremediation” on
page 309), these technologies can both boost the
recovery of metals from ores and remove water
contaminants. Of particular value to mining firms is their
potential to recover metals from sub-marginal ore.
The bacteria involved, primarily species of Acidithiobacillus,
Leptospirillum, and Sulfobacillus, obtain their energy byusing enzymes to oxidize iron and sulfur compounds in
the presence of water and atmospheric gases. Part of
Alison’s research involves experiments designed to
determine how much metal sulfide the bacteria can
oxidize per unit of time. Mining companies would like
to know more about these enzymes and the molecular
genetics behind them. A logical first step is to identify
the genes involved.Unlocking Molecular Mysteries
One approach is to clone these genes and then use them
to replace their counterparts in other bacteria whose
genetics are well known. Plasmids of Acidithiobacillus
have thus been introduced into E. colito enable the
expression and regulation of Acidithiobacillusgenes to be
studied. For example, the recA gene in E. coliproduces
a protein that repairs DNA damage. (For more on DNA
damage, see Chapter 9.) By replacing recA with its
counterpart from Acidithiobacillus, researchers discovered
that the foreign gene could also carry out some DNA
repairs. However, cloned genes may be expressed
differently in the host bacterium than they are in the
parent. This approach also cannot be used to study
genes not represented in the host bacterium, such as
those for iron or sulfur oxidation.
Alison’s goal is to unlock some of the molecular mysteries
behind the bio-leaching bacteria, thereby helping to make
the new mining technologies they promise economically
viable. Mining firms could then operate at lower costs
while posing a significantly reduced environmental risk.Career Tips
To become a molecular biologist, you will need to excel
in courses in cellular biology and biochemistry in your
undergraduate studies. You will then have to complete
a master’s degree or doctorate in the field.Prokaryotic cells have an extra advantage in
accelerating the rate of protein synthesis. While
the basic principles of translation are the same in
prokaryotic and eukaryotic cells, there is one key
difference. In a prokaryotic cell, the mRNA transcript
extends directly into the cytoplasm of the cell as
it is being formed. This means that ribosomes can
bind to the mRNA even before transcription is
complete, allowing transcription and translation
to take place on the same mRNA strand at once,
as shown in Figure 8.23. In a eukaryotic cell, in
contrast, the processes of transcription and
translation are physically separated by the
membrane of the nucleus.A computer uses binary processing technology, so named
because it stores information in the form of long sequences
of just two digits, 0 and 1. These linear information
sequences are translated into the text and graphics you
see on your screen and the sounds you hear from your
speakers. In comparison, the genetic code stores
information using four“digits.” Thus, the information-
coding properties of DNA are much more powerful than
those found in binary processing technology. A DNA-based
computer the size of a lump of sugar could contain more
information than a trillion CDs.