Biology Reference
In-Depth Information
Modes of mutagenesis in flies (as applied to miRNA loci)
A Chemical
C Imprecise
P
element excision
P
element
*
(
)
(
Change important nucleotides (very rare)
)
(
)
Mostly unidirectional deletions uncovered
from ~10% of P excisions that are imprecise
B Transposon insertions
P
element
D FRT-mediated deletion
>FRT
Interfere with transcription start (mostly)
Hotspots (e.g., P) often identify promoters
>FRT
piggyBac, Minos
Flp-mediated
recombination
(
)
Other transposons with less insertion bias
Defined deletion leaving behind 1 FRT site
E Gene targeting by homologous recombination
white
Knockout of miRNA hairpin
insertion of marker gene (e.g.,
white+
for eye pigment)
white
F Genomic engineering
Rescue miRNA
modified miRNA
Nuclear marker
nDsRed
Membrane marker
Gal4 driver
CD8-
GFP
Gal4
Figure 8.1
Making fly miRNA mutants. The major methods for generating mutations
in fly miRNA loci are described. (A) Chemical mutagens, though very useful for
generating mutant alleles of protein-coding genes, have been of limited use in investi-
gating Drosophila miRNA genes. The only published example is a point mutant in
miR-278 that was recovered as a revertant of a gain-of-function phenotype (see
Section 3.1
). (B) Transposon insertions can interfere with transcription and therefore
