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Figure 9.25
Evolution of the micronuclear
TP gene of
Sterkiella histriomuscorum
from the
α
TP gene of
Sterkiella nova
/
Stylonychia mytilus
by insertion of three more
internal eliminated segments, creating three more macronuclear destined segments.
From Prescott et al. [12].
α
The gene in the third species,
Sterkiella histriomuscorum
, contains three
additional IESs and MDSs. MDS 13 in
Sterkiella nova
and
Stylonychia mytilus
is split into three MDSs in
Sterkiella histriomuscorum
by insertion of two IESs,
and MDS 8 has been split into two MDSs by insertion of an IES, as illustrated
in Figure 9.25.
A diagram of 14 MDSs, with their incoming and outgoing pointers, in the
micronuclear
TP gene of
Sterkiella nova
or
Stylonychia mytilus
is shown in
Figure 9.26. Eleven of the 13 pairs of pointers encompass overlapping seg-
ments of DNA (e.g., the pair of P2 pointers encompasses a segment of DNA
that overlaps with DNA segments encompassed by the pointer pairs P3, P4,
P5, P6, P7, P8, P9, P10, P11, and P12). Thus, a series of six dlad excision
operations will rearrange MDSs 1 through 12 into the orthodox order. Two ld
excision operations join MDSs 12, 13, and 14, completing assembly of the
α
α
TP
gene in
Sterkiella nova
and
Stylonychia mytilus
. The
α
TP gene in
Sterkiella
Figure 9.26
A diagram of the 14 macronuclear destined segments (MDSs), with their
pointers, of the micronuclear
α
TP gene in
Sterkiella nova
and
Stylonychia mytilus
.
MDSs are numbered in the open blocks. Internal eliminated segments (not numbered)
are lines connecting MDS blocks.
