Biology Reference
In-Depth Information
amount of coding DNA among the 12 species varies by approximately 1.7-fold,
ranging from 111Mbp in
D. simulans
to 187Mbp in
D. willistoni
. The genomes
are contained in six homologous chromosome arms, and the genes within the
arms are largely conserved among the
Drosophila
species evaluated. Within
each arm, however, the order and orientation of the genes can vary due to gene
rearrangements caused by a large amount of gene movement by TEs. The com-
parisons of specific genes indicated that 11.9% of all new genes found were due
to development of a totally new gene (not due to gene duplication). This indi-
cates that novel genes provide novel aspects of
Drosophila
species' biology. A
great deal more was learned from these evaluations, including how to improve
alignment and comparison methods.
7.21 Interactomes or Reactomes
Now that genomes have been sequenced and studied intensively, it is apparent
that learning the DNA sequence is the first step in understanding the biology
of an organism (
Nature Biotechnology
2011
). Researchers are now attempt-
ing to build networks of protein-protein interactions as a method for under-
standing signaling cascades and mechanisms of cell biology. Understanding how
genes, and their proteins, work in pathways is now the goal (
Beloqui et al. 2009,
Bonetta 2010
).
7.22 The Post-Genomic Era: Systems Genetics
During at least the past 50 years, biology was dominated by a reductionist
approach, which narrowed the focus from the entire animal in its natural envi-
ronment to increasingly smaller parts. The enormous complexity of a living
organism overwhelmed the ability of biochemists, cell biologists, structural biol-
ogists, physiologists, and geneticists to study the whole animal (
Vukmirovic and
Tilghman 2000
). Studies of organs, then cells and, finally, individual molecules
became the focus of analyses.
The reductionist approach will continue to be productive, and necessary, to
obtain detailed knowledge about gene function, gene regulation, and gene
sequences of the genomes of organisms. One example of a sophisticated reduc-
tionist approach is the sequencing of the genomes of multiple individuals in a
population to quantify molecular genetic variation. For example,
Mackay et al.
(2012)
produced the
Drosophila melanogaster
Genetic Reference Panel, consisting
of the genome sequences of 168 inbred lines derived from a natural population
in North Carolina. The goal is to learn about quantitative traits, and the panel of
fly lines is being made available to all geneticists interested in complex traits.
