Research
Most plants and animals have two copies of each chromosome in
the normal chromosome set. Unbalanced numerical changes
resulting from gains or losses of individual chromosomes
(aneuploidy) usually have deleterious consequences. For
example, Down syndrome in humans is caused by an extra
(triplicate) copy of chromosome 21. Human tumor cells usually
display numerous alterations in chromosome number and
structure. Little is known about how changes in chromosome
number influence gene activity and chromosome integrity,
thereby perturbing physiology and development.
The current literature, moreover, seems to be divided regarding the
question whether in an organism with an extra chromosome most
of the genes on the extra chromosome reflect the dosage
increase. In such assessments, classical analyses face the
problem that a large number of genes change in an asymmetric
way, invalidating most commonly used normalization
approaches. Using appropriate transforms, however, we could
show in Huettel et al. (2008) that most genes indeed reflect
the dosage increase, with only a small percentage being
regulated differentially from this trend.
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