Transcript lecture3

• What did you learn from surfing FlyBase?
• Why do the inversions in Balancer
chromosomes greatly reduce the frequency
of crossing over in meiosis?
• Autonomous vs non autonomous
• Domineering - mutant cells disrupt the
development of neighboring wild type cells.
• Submissive - wild type neighbors rescue
mutant cells.
• FLP/FRT can also be used to remodel
RNAi in flies
ds RNA in cultured cells.
RNAi in flies
1. Express a fold back RNA from a transgene.
2. This results in tissue/temporal specific gene knockdowns.
3. Collections of transgenic flies are available that contain
transgenes to knockdown the expression of most fly
Gene targeting
• Until recently not available in flies.
• One difficulty is that one cannot select for a
targeted cell.
• A technique has now been developed that
has been shown to work on a number of
• Technique requires first getting a germ line
transformant for the knock out construct.
• The DNA for targeting is excised by the
activity of the FLP/FRT site specific
recombination system.
• The excised circle is then cut by the induced
expression of a very rare cutting RE.
• High rate of homologous targeting.
In Vivo Imaging
• A number of developmental stages/tissues
provide opportunities for in vivo imaging.
Genetic Screens
• Recessive lethal mutations
The isolation of recessive visible mutations
mutagenize th st
fz in ri/TM3
screen for flies that are phenotypically fz or in.
these flies would be fz*th st/fz in ri or th st in*/fz in ri
The isolation of recessive lethal mutations
cn bw
cn bw
cross siblings
treat with mutagen (e.g. ems)
X Gla/CyO
cn bw/CyO
cn bw/CyO
X Gla/CyO
cn bw/CyO
cn bw/ cn bw
cn bw/CyO
Look for vials with no straight winged flies
• High efficiency of FLP/FRT clone induction
has allowed new types of mutant screens.