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observations had suggested [3,4] . Two sets of key obser-
vations stand out. First, each chromosome occupies its own
territory, with only limited intermingling ( Figure 7.1A ).
Second, individual loci are often positioned non-randomly
with respect to the nuclear periphery.
Over the past decade, several new technological
developments have made it possible to study the molecular
composition and the spatial architecture of chromosomes.
On the one hand, new molecular mapping techniques have
begun to yield genome-wide datasets that describe the
localization of proteins and modifications along chromo-
somes as well as spatial folding of chromosomes in
unprecedented detail. On the other hand, theoretical models
and simulations
can provide understanding of
the
(A)
(B)
Structure population
1
2
3
4
10,000
Sample structure from population
Chromosome
territories
1
ยต
m
(C)
NPC
NL
FIGURE 7.1 Spatial organization of chromosomes: data and models. (A) FISH painting of chromosomes. Each chromosome is labeled with
a different color (image from [5] , reproduced with permission). Note that the chromosomes each occupy a distinct territory. (B). Computational model of
chromosome organization based on genome-wide chromatin interaction data [6] . Chromosomes are labeled in different colors. (C) Cartoon model of
chromosome organization in a nucleus. Two chromosomes are indicated in purple and brown. Transcriptionally inactive chromatin (thick lines) tends to
aggregate near the nuclear lamina, NL, (green); regulatory regions and active genes (thin lines) may be brought together in the nuclear interior by specific
protein complexes (yellow and orange circles). NPC, nuclear pore complex. (Adapted from [7] ).
 
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