Biology Reference
In-Depth Information
Fig. 3.
Comparison of gene repertoires of 5 insect and 5 vertebrate genomes, ranging
from the core of metazoan genes (black fraction on the left) to the species-unique
sequences (white band on the right). The striped boxes correspond to insect- and
vertebrate-specific orthologous genes, where the darker band corresponds to all
insects or vertebrates (allowing one loss). “N:N:N” indicates orthologs present in
multiple copies (allowing one loss), and “Patchy” indicates ancient orthologs (requir-
ing at least one insect and one vertebrate gene) that have been differentially lost in some
lineages. The species tree on the left was computed using the maximum-likelihood
approach on concatenated alignments of single-copy orthologs, and it shows an
accelerated rate of evolution in insects.
of somewhere between 40% and 75% of bilaterian genes are thought to
undergo alternative splicing, with some genes coding for thousands of
transcripts. However, human and rodent comparisons revealed at least a
quarter of human splice variants that are not present in their orthologous
mouse genes, and species-specific isoforms are present for about half
of the alternatively spliced genes,
47
suggesting that these noncon-
served isoforms may be due to “splicing noise” (or aberrant splicing).
48
Nevertheless, experimental verification has shown support for many minor
