EvoluTion And dEvEloPmEnT 377
(alternative splicing). As we discussed in C hapter 14, a large fraction of genes may
have alternatively spliced transcripts (isoforms), and the number of isoforms can be
very high. These processes are becoming subjects of active evolutionary research.
In interactions among cells, such as those that underlie tissue induction, mol-
ecules released by one cell type diffuse and are bound by the extracellular domain
of receptor proteins that span the membrane of other cells. This changes the con-
figuration of the protein’s intracellular domain, which sets off a signal transduction
cascade of protein interactions in the receiving cell, and that may end by activat-
ing dormant transcription factors and changing which genes are transcribed in the
cell. BOX 15A describes some of the methods used to study gene expression during
development.powerful base of knowledge for studies in evolution-
ary genetics and evolutionary developmental biology.
These data are available in public online databases
such as FlyBase (http://flybase.org) for Drosophila
melanogaster and several other databases, such as
ENCODE (www.encodeproject.org), for humans. As
genomic and transcriptomic data from more species
are accumulated and compared with the comprehen-
sive information on model species, more and more
investigations of the evolution of species differences
become possible.BOX 15A
Some Methods in Developmental Genetics (continued)
Futuyma Kirkpatrick Evolution, 4e
Sinauer Associates
Troutt Visual Services
Evolution4e_Box15A_Fig1.ai Date 12-21-2016(A)FIGURE 15.A1 Some methods of studying gene expres-
sion in developing animals. (A) CRISPR-Cas has been used
to knock out function of various Hox genes in the crustacean
Parhyale, resulting in homeotic transformation of certain
appendages into other appendages. Normal and trans-
formed appendages are shown in the scanning electron
micrographs. Thoracic and abdominal segments are labeled
T and A, respectively. Appendages on segments T6, T7, and
T8 are colored in a wild-type (WT) larva (left photo), and the
transformation of these to a T4 or T5 morphology (colored as
in the wild type) is shown in a larva in which the abdA Hoxgene was knocked out (right photo). (B) The top photo shows
fluorescent antibody staining of the proteins Yellow (in green)
and Ebony (in purple) in the pupal wing of a male Drosophila
biarmipes. The bottom photo shows the ebony gene ex-
pressed (as protein) where the pigmented spot is located in
the fully developed wing. (C) Green fluorescent protein (GFP)
expression (bright green) by a transgenic reporter construct
containing cis-regulatory DNA from a gene that is expressed
in the pharynx of the nematode Caenorhabditis briggsae.
(A from [42]; B, photos by John True; C, photo by Eric Haag,
courtesy of Takao Inoue and Eric Haag.)Futuyma Kirkpatrick Evolution, 4e
Sinauer Associates
Troutt Visual Services
Evolution4e_Box15A_Fig1BC.ai Date 12-21-2016(B) (C)15_EVOL4E_CH15.indd 377 3/22/17 1:30 PM