Chapter 9 pt 1 Flashcards
The chief advantage of Drosophila initially was one that historians have overlooked: it was an excellent organism for _______
student projects
- Robert E. Kohler
Genus: Drosophila
Species: _______
melanogaster
Drosophila were used as a study system because they were:
1) easy to _______
2) _______ sequenced
3) large and freely available mutant _______
4) well developed exchange and sharing _______ of researchers
1) breed
- easily observed polytene chromosomes
2) genome
3) database
4) network
Drosophila undergo _______ development
syncytial
- karyokinesis without cytokinesis until after 13th division
in drosophila, A/P and D/V axis are specified _______ by interactions within the egg and between the egg and surrounding follicular nurse cells in the ovary.
(WHEN?)
prior to fertilization
in drosophila development, supporting _______ cells produce and deposit mRNA’s into the oocyte cytoplasm
nurse
In drosophila, egg activation occurs _______ the sperm contact the egg. It occurs during _______
before
ovulation
physical compression of the egg as it is laid opens Ca2+ channels allowing Ca2+ to flow in, which _______ and allows _______ before fertiliztion
initiates protein synthesis
egg to resume meiosis
What mechanism in drosophila eggs ensures monospermy?
micropyle
- only 1 sperm can enter at a time
- only at 1 point
Drosophila undergo _______ cleavage
meroblastic centrolecithal
- large centrally located yolk inhibits cleavage except at the rim of the egg
cleavage:
rapid nuclear division creates a _______
syncytium
cleavage:
During the 9th division, 5 nuclei move to the posterior pole becoming _______ that will form the _______ in the adult
polar cells
gametes
cleavage:
During the 10th division, the remaining nuclei move to the _______, where they divide ___ more times, more slowly than the 8 minute average up to this point
periphery
3
Syncytial blastoderm in cleavage:
_______: cytoskeletal components and cytoplasm that surround each nuclei
energid
Cellular blastoderm in cleavage:
After the 13th division, the plasma membrane fold _______ between the nuclei, pinching off each nuclei into a single cell
inward
- accompanied by dramatic changes to cytoskeleton
_______: When cell divisions become asynchronous and slower/variable
- where cellularization occurs
mid-blastula transition
When does mid-blastula transition occur?
14th division
- cellularization occurs
_______ is the first real point at which the zygote genome is needed
mid-blastula transition
aka maternal zygote transition
- they can be interchanged with each other
_______: when control is shifted from maternally supplied mRNA’s and proteins to the zygote genome
Maternal to Zygote Transition (MZT)
- maternally supplied mRNA’s are degraded/zygotic genes are activated
_______ is a maternally supplied RNA binding protein that represses translation
Smaug
How does Smaug repress translation?
slowly translated and builds up then targets other maternal mRNA for destruction
- as more gets translated, more maternal mRNA is destroyed
_______ is another maternally supplied mRNA that binds to CAGGTAG motif in early zygotic genes, activating transcription
Zelda
What does Zelda stand for?
Zink-finger Early Drosophila Activator
During gastrulation and segmentation what parts are formed? (shortly after cleavage)
1) head
2) 3 thorax segments
3) 8 abdominal segments
3 thorax segments will form:
1) first: _______
2) second: _______
3) third: _______
1) legs only
2) legs and wings
3) legs and haltares (balancers)
Explain A/P formation during oogenesis
1) Gurken mRNA is localized between the oocyte nucleus and cell membrane and translated into Gurken protein
2) Terminal follicle cells translate torpedo gene to produce torpedo receptors to receive gurken protein
3) Terminal follicle cells differentiate into posterior posterior follicle cells
4) gurken signal activates PKA and Par-1 in PFC’s that orient microtubules (+ growing end @ posterior)
5) Bicoid mRNA moved to anterior (-) end by dynein
6) Oskar mRNA moved to posterior (+) end by kinesin I
7) Oskar protein is translated and binds to nanos mRNA, localizing it to the posterior end as well. also recruits more PAR-1
_______ is localized between the oocyte nucleus and cell membrane where it is translated into _______
Gurken mRNA
Gurken protein
Gurken signal is received by a receptor translated from the _______ gene
torpedo
Terminal follicle cells receiving the Gurken signal differentiate into _______
Posterior follicle cells (PFC)
The gurken signal activates _______ and _______ in posterior follicle cells that orient microtubules with their + (growing) end at the posterior
PKA and Par-1
Maternally supplied _______ binds to _______ and is moved towards the anterior (-) end of the oocyte
bicoid mRNA
dynein
Maternally supplied _______ binds to _______ and is moved towards the posterior (+) end of the oocyte
Oskar mRNA
Kinesin I
Oskar binds to the _______ localizing it to the posterior end as well, Oskar also recruits more _______ which stabilizes more microtubules and amplifies the signal
nanos mRNA
PAR-1
Movement of oscar and bicoid creates a localized difference in cytoplasm contents that will eventually produce the _______ that will determine the abdomen and germ cells
pole plasm
Segmentation depends on the hierarchy of genes and TF’s established and positioned along the _______ axis
anterior/posterior
What are the 5 stages of hierarchy of genes that affect segmentation?
1) maternal effect genes
2) gap genes
3) pair-rule genes
4) segment polarity genes
5) homeotic selector genes
_______: maternally supplied (ex bicoid and nanos)
maternal effect genes
_______: zygotic genes activated or repressed by bicoid and nanos
gap genes
- broad 3-segment regions
_______: zygotic genes activated or repressed by the protein products of gap genes and maternal effects genes
pair-rule genes
- produce TF in 7 focused bands
_______: zygotic genes activated or repressed by pair-rule gene protein products
segment polarity genes
- establishes segments (14)
_______: zygotic genes regulated by segment polarity gene protein products
homeotic selector genes
- determines the strucutres
Bicoid mRNA is actively transported to the anterior end of the oocyte prior to fertilization and requires interaction of its 3’-UTR with _______ and _______ to be transported
Exuperantia
Swallow
Nanos mRNA becomes trapped at the posterior end through interactions between its 3’-UTR and 5 proteins, what are the 5 proteins?
1) Oskar
2) Staufen
3) Valois
4) Vasa
5) Tudor
non-trapped nanos mRNA in the cytoplasm is bound by _______ and _______ that prevent its translation through association with 3’-UTR
Smaug
CUP
- Oskar can break this complex up at the posterior end
_______ and _______ are maternally supplied and found throughout the oocyte’s cytoplasm. Their translation is affected by bicoid and nanos proteins after fertilization
Caudal (cad)
Hunchback (hb)
Bicoid protein inhibits _______ translation
caudal mRNA
Nanos protein inhibits _______ translation
hunchback mRNA
