What is aneuploidy?
To reproduce themselves accurately, cells must do two things: (1) make
a copy of all their DNA (
replication) and (2) evenly
separate each copy into the new daughter cells (
mitosis).
Cells can do this with remarkable accuracy.
However, mistakes do happen. Yeast cells, for example, fail to separate
chromosome copies once every 10,000-1,000,000 cell divisions. When this
happens, each daughter cell obtains a different set of chromosomes than
the parent cell: one daughter will be missing a chromosome and the
other daughter will have mistakenly received that chromosome, making it
an extra one. This chromosomal state is called
aneuploidy.
Aneuploidy can affect the health or the
"phenotype" of cells and organisms.
Down
syndrome, for example, results when a child receives one extra
chromosome. But in some environments, the effects of aneuploidy might
give cells particular growth advantages. For instance, cancer cells
that can outgrow their neighbors frequently have aberrant numbers of
chromosomes. Yeast cells grown many generations in a laboratory can
sometimes become aneuploid or exhibit chromosome rearrangements.
Are aneuploidies related to growth advantages in these cases? Or are
they byproducts of some other problem in the cell? How exactly does an
extra chromosome affect a cell?
These are the kinds of questions we
want to answer. To do so, we are engineering strains of yeast where
the
only difference between them will be the presence of an
extra chromosome. We are studying these strains to characterize and
document how they differ from normal yeast cells.