Obtaining Molecules 
for Study 
To a large extent, the 
progress made since the 
1950’s in all areas of 
biology has been depen- 
dent on the development 
of techniques to obtain, 
grow, and purify suffi- 
cient quantities of specific 
types of cells and mole- 
cules, as well as to 
separate cellular compo- 
nents in centrifuges. In 
the late 1960’s, 
scientists devised reliable 
methods of growing cells 
in the laboratory. 
Eventually, they also 
learned how to grow cells 
in various chemically 
defined solutions. These 
advances allowed 
researchers to study and 
compare biochemical 
processes in different 
types of cells and to 
determine the molecular 
details of many complex 
cellular activities. 
Major improvements have 
also been made in sorting 
proteins and nucleic 
acids. A technique called 
column chromatography 
separates fragments of 
nucleic acids or proteins 
according to their size, 
electrical charge, and 
other important charac- 
teristics. This process uses 
a hollow column that is 
filled with a material 
through which the mole- 
cules in a solution move 
at different speeds. This 
allows a researcher to 
