Final Flashcards
Is bicoid haplosufficient or haploinsufficient? What does this mean?
It is haplosufficient and therefore only one functional copy of the gene is required for normal function
What is the Dorsal vertebrate homologue?
NF kB TF
nuclear factor kappa beta transcription factor
What is the Toll vertebrate homologue?
Toll-like receptors
What is the Gurken vertebrate homologue?
Epidermal Growth Factor (RTK ligand)
What is the Torpedo vertebrate homologue?
Epidermal Growth Factor receptor (RTK)
- Important in immunology
What is the Dpp vertebrate homologue?
Dpp = decapentaplegic
Homologue is BMP (paracrine factor)
What is the Sog vertebrate homologue?
Sog = short gastrulation Homologue = chordin
A BMP inhibitor
What is Twist?
A gene in flies that codes for a TF. The TF is necessary for mesoderm development
Dorsal turns on Twisted gene in the ventral part of the embryo (normally)
What cells express the Torpedo (Epidermal Growth Factor receptor) in fly development?
The dorsal follicle cells
What ligand binds to Torpedo receptors?
Gurken binds Torpedo on follicle cell membranes
Torpedo is a receptor tyrosine kinase
Why isn’t Gurken in the ventral side of the embryo?
It’s mRNA was associated with the oocyte nucleus that was transported to dorsal, anterior portion of the nucleus - Once translated it diffuses, but the distance is too far for it to reach the ventral side
Pipe
An enzyme made by the follicle cells
- Sulfates ventral vitelline proteins
Synthesis of Pipe is inhibited by RTK signalling (Gurken binding Torpedo on dorsal follicle cells)
What are the three proteases in the big fly developmental pathway?
GD (gastrulation defective), Snake, Easter
Snake and Easter are zymogens
What happens when cactus is phosphorylated?
It will be degraded and dorsal is then free to move into the nucleus
What does the tube protein do?
It is an adaptor protein that helps Pelle bind the Toll-receptor
What is the vertebrate homologue protein to Pelle?
IRAK
Interleukin Receptor-Associated Kinase
Examples of BMP inhibitors?
Sog (flies), Chordin, Follistatin, Noggin, etc
What does the blastocoel ensure during development?
It provide space between groups of cells to prevent mesoderm inducing signals from reaching the ectoderm.
capacitation
The physiological changes the sperm must undergo within the female reproductive tract to become competent to fertilize an egg
- sperm must last 6 hours in the female before reaching the egg
- binds to cells in the oviduct and becomes hyper activated
- (bicarbonate, calcium - activate pKA)
What is the zona pellucida?
Layer that surrounds the plasma membrane of the egg and early embryo. It consists of glycoproteins and proteins (ZP2 in humans where sperm binds)
Sperm binds here to begin fusion
What is the acrosome reaction?
When the contents of the acrosomal vesicle are expelled through exocytosis - allowing sperm penetration and digestion through the zona pellucida
Exposes the proteins on the acrosomal membrane to the outside (of the plasma membrane. This allows interaction of Izumo with Juno and CD9
What is the receptor for Izumo and where does this binding occur in the body?
Juno/CD9 is the receptor for Izumo and these proteins are present on the plasma membrane of the egg.
Izumo is present on the acrosomal membrane, and then the PM after the acrosomal reaction, in sperm.
Juxtacrine interaction
What protein does the sperm bind to on human zona pellucidas?
ZP2 protein
ZP3 in mice
How is polyspermy blocked in humans?
Enzymes released through the cortical reaction.
Here, ZP2 protein on the zona pellucida is cleaved so that it can no longer bind sperm.
What stage of meiosis in the egg paused in right before fertilization?
metaphase 2
Where does fertilization most often occur?
In the ampulla, but it can occur in the infundibulum
infundibulum
Part of the oviduct where fertilization can occur. However, it more often occurs in the ampulla
Amount of sperm in ejaculate versus the amount that get to the egg?
300 million versus 200
Where do sperm develop?
In the seminiferous tubules. Generated from puberty to death in males.
Acrosomal vesicle
Developed ventrally on the spermatid. It is a modified Golgi apparatus that contains proteolytic enzymes necessary to digest the zona pellucida surrounding the egg
Where are the mitochondria on the spermatid?
On the base of the head. They generate ATP that the sperm can use for movement
What is the germinal vesicle?
The large diploid nucleus of the primary oocyte (before meiosis)
Where are the cumulus/granulosa cells?
surrounding the zona pellucida
Chemical processes in sperm capacitation?
Bicarbonate influx causes activation of SACY - SACY then generates cAMP that activates PKA. PKA phosphorylates tyrosine kinases which phosphorylate sperm proteins – sperm is capacitated!
How many types of glycoproteins are present on the surface of the zona pellucida and which one is active in binding sperm?
There are four: ZP1-4.
ZP2 is the only one active in binding sperm.
What must occur for Izumo to be able to bind to Juno/CD9?
Exocytosis of the Izumo ligand present on the acrosomal membrane of sperm to the plasma membrane of sperm
What proteins are necessary for fertilization to occur?
Izumo ligand, Juno and CD9 (complex of receptors for Izumo)
Polyspermy Block in Humans
Membrane fusion between the sperm and the egg triggers exocytosis of cortical granules by the egg (the cortical reaction)
- digestive enzymes are exocytosed in the cortical granules and they cleave the ZP2 proteins on the surface of the zona pellucida
- This blocks anymore sperm from binding.
Does a change in membrane potential occur in the human block to polyspermy?
NO
This is part of the mechanism for the fast block to polyspermy seen in sea urchins. Fast block is not necessary as their is less sperm competition in mammals
Cortical Reaction
Exocytosis of cortical granules from the egg that occurs when the sperm fuses with the egg.
The vesicles which are exocytosed contain digestive enzymes that cleave the ZP2 proteins present on the zona pellucida.
Because ZP2 proteins are necessary for sperm binding, cleavage of these proteins blocks any more sperm from binding.