Biology Reference
In-Depth Information
Figure 1.1 Mouse hemi-mandible (left) with 11 left-sided landmarks shown in place.
The landmarks are by number: 1, coronoid process; 2, mandibular angle; 3, anterior-most
point on mandibular condyle; 4, posterior-most point on mandibular condyle; 5, superior-
most point on inferior border of mandibular ramus (joining of angular notch with cor-
pus); 6, inferior-most point on border of ramus inferior to incisor alveolar; 7, inferior-most
point on incisor alveolar rim (at bone-tooth junction); 8, superior-most point on incisor
alveolar rim (at bone-tooth junction); 9, mandibular foramen;10, anterior point on molar
alveolar rim; 11, intersection of molar alveolar rim and base of coronoid process.
Bilateral right-sided points are numbered landmarks 12-22.
expressed patterns of craniofacial dysmorphology. Many genes are
conserved across mammals, and the proximate functions of those genes
are likely to be conserved as well. We asked whether a conserved
phenotypic response could arise from a similar complex genetic insult
in humans and mice using the Ts65Dn mouse (Richtsmeier and Baxter
et al., 2000). If dysmorphic craniofacial phenotypes are common to
Ts65Dn mice, then they can be used to understand the processes by
which trisomy for particular genes results in the development of cran-
iofacial dysmorphology.
The Ts65Dn data set consists of landmarks collected from mandibles
of aneuploid Ts65Dn mice and euploid littermates. Three-dimensional
coordinate locations of 22 mandibular landmarks ( Figure 1.1 ) were
recorded using the Reflex microscope (see Chapter 2 for discussion of
the instrument for data collection). The analysis of the original data set
showed that the crania (including the mandible) of the Ts65Dn mice are
significantly different from crania of their normal littermates in ways
reminiscent of the difference between the skulls of normal children and
those of children with DS (Richtsmeier et al., 1999).
1.3.2 Data set 2: Craniofacial growth in monkeys
The study of growth has long been of interest to biologists. Growth of
the skull requires a complex coordination of changes in individual
bones as the skull keeps pace with the growing soft tissue organs and
Search WWH ::

Custom Search