drosophila Flashcards
how long is the drosophila life cycle at 25 degrees
10 days
DEFINE: heredity
the genetic transmission of characteristics from parent to offspring
the drosophila genome consists of 143,726,002 bp. there are 137.6 million bp on the 7 chromosome arms. where are the remaining 1.5 million bp located?
heterochromatin regions
is drosophila courtship innate or learned behaviour?
innate
- isolate flies for a long period of time then expose to flies —> courtship behaviour occurs
describe the process of spermatogenesis
- tip of testes contains hub cells
- hub cells secrete factors (e.g. unpaired) promoting stem cell fate
- stem cells adjacent to hub + surrounds the hub
- cells further away from the hub differentiate into somatic cyst cells ——-> sperm
what is endo-reduplication?
dna replication without cytokinesis
which part of the ovary stores sperm in drosophila?
seminal receptacle
stem cell maintenance in ovarioles
- stem cell undergoes 4 cystoblast mitotic divisions
- selection of future oocyte and nurse cells
- egg activation by meiosis I and II
- sperm fuses with female pronucleus of oocyte
what are nurse cells?
huge support cells in the ovarioles that undergo endo-reduplication —> contains many genome copies —-> maternal contributions
polytene chromosomes
sister chromatids lying parallel to each other as a result of duplicated dna not being separated into separate cells
describe the process of cytoplasmic dumping in the ovarioles
- nurse cells’ cytoplasm is packed with maternal gene products and proteins
- mRNAs and proteins e.g. oskar move from nurse cells into developing oocyte via ring canals
- nurse cells shrivel and die
what are ring canals?
holes linking up nurse cells
how does the subcellular localisation of maternal factors occur?
localised by cytoskeleton - maternal factors are transported via microtubule transport using + and - ended motors
describe early embryonic developmental processes of drosophila embryo
- male and female pronucleus fuse
- nucleus divides for 14 stages without egg division (using materials laid down by nurse cells) —> results in syncytium
- nuclei migrate to periphery of cytoplasm. few nuclei remaining in the middle end up in yolk.
- each nucleus separates into their own cell to form somatic nuclei
DEFINE: imaginal discs
structures of columnar epithelial cells remaining diploid throughout larval development. where most adult tissues arise from.
where is patched expressed on the wing imaginal disc?
on the boundary between the anterior compartment and posterior compartment
where is wingless expressed on the wing imaginal disc?
dorsal-ventral boundary of wing disc
what is engrailed and what is its role in patterning the wing?
- transcription factor located in nucleus
- expressed in posterior compartment of wing imaginal disc
- drives Hh expression
- suppresses Ci expression so prevents cells in posterior compartment from responding to Hh signalling
describe the dpp signalling pathway
- dpp binds to tkv and pnt
- mad TF phosphorylated and activated
- phosphorylated Mad acts on promoters of target genes
activates transcription of omb and sal
represses transcription of brinker
low concentrations of dpp induce……
omb expression - broader pattern
no sal expression
DEFINE: nanobody
single chain amino acid made by cammelids
describe the process of making a morphotrap for dpp
- labelled dpp with GFP
- expressed membrane tethered anti-GFP
- antibodies trapped dpp-GFP on the membrane –> stops gradient formation and restricts dpp expression to midline
what will be observed when a clone of cells lacking engrailed expression is made in the posterior compartment?
- ci is made because its suppression is released
- hh diffuses into patch of cells
- dpp expression observed around the patch of cells = ectopic midline
what will be observed when a clone of cells expressing engrailed is made in the anterior compartment?
- engrailed drives hh expression
- cells expressing ci surround the patch of cells and respond to the ectopic hh signal
- ring of dpp expression around patch of cells observed - ectopic midline
what will be observed when a clone of cells lacking patched expression is made in the anterior compartment?
- inhibition of smo released —> smo activated
- dpp activated –> dpp expression inside clone of cells
- dpp diffuses out and patterns both ways
mirror image symmetry of anterior wing
what will be observed when a clone of cells lacking patched expression is made on the midline?
hh diffuses away and binds to ptch receptors on WT ligand
what is an enhancer trap?
technique used to visualise gene expression - promoter trapping
what are ovarioles
each ovary contains ovarioles
ovarioles = where eggs develop
what is a chorion?
egg shell secreted by follicle cells
what is the vitelline membrane?
hydrophobic membrane under chorion protecting from drying out
what would be observed in a mutant stat92e drosophila embryo
gaps in a4 and a5
problems with head segment and posterior segment
