often readily transferable to human biology. Yeast 
has also proved to be an excellent host for the propa- 
gation of large segments of cloned human DNA. Dr. 
Olson's laboratory has developed a high-resolution 
map of the DNA normally present in yeast cells and 
is cooperating with other groups involved in yeast 
research to promote the use of such maps as major 
tools in genetics research. His laboratory is also con- 
tinuing to develop appUcations of yeast-based clon- 
ing systems to human genetics. The use of sequence- 
tagged sites (STSs), landmarks within human DNA 
that can be completely described in an electronic 
database, has received particular attention. STS- 
based mapping of human DNA cloned into yeast is 
finding wide applications in the international effort 
to map the human genome. Finally, studies of the 
reintroduction of DNA into mammalian cells, fol- 
lowing propagation in yeast, are under way; this ex- 
perimental procedure offers a path to the functional 
analysis of the cloned DNA. 
A major project of the laboratory of Assistant In- 
vestigator George M. Church, Ph.D. (Harvard Medi- 
cal School) is the development of technologies for 
analysis of genomes in order to compare them for 
conserved and variable genetic elements. These 
technologies include nonradioactive chemilumines- 
cent multiplex sequencing; REPLICA automated se- 
quencing, reading, and comparison software; in 
vivo footprinting; and subtractive sequencing. 
These methods are being applied to the develop- 
ment and correlation of whole genome databases 
of DNA polymorphic sites, protein termini, pro- 
tein abundances, and interactions among cellular 
components. 
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