fertilisation

Question 1

where do sperm undergo maturation?

Answer 1

in the epididymis

Question 2

what happens for the sperm to mature?

Answer 2

further fluid absorption, secretions include fructose, proteins and glycoproteins, results in transfer of proteins onto PM of sperm to increase fludity, acquire the ability to swim progressively

Question 3

how do sperm acquire the ability to swim progressively?

Answer 3

through a more rigid flagellum and increased cAMP content in the tail

Question 4

where does capacitation take place?

Answer 4

in the female tract

Question 5

what are the main characteristics of a fully capacitated sperm?

Answer 5

hyperactivated motility, changes in membrane properties that allow the acrosome reaction to happen, more responsive to signals from oocyte

Question 6

what happens in capacitation?

Answer 6

strip/modify surface glycoproteins, loss of cholesterol reduces membrane stability

Question 7

how does the hyperactive motility occur?

Answer 7

sperm cytoplasm becomes more alakaline, this increases calcium permeability and intracellular calcium conc, results in increased adenylate cyclase activity- activates PKA and downstream signalling pathways

Question 8

what is hyperactive sperm motility?

Answer 8

high amplitude, asymmetrical beating of the flagellum- helps sperm reach its target and penetrate into zona pellucida

Question 9

what are the survival times for sperm and eggs?

Answer 9

6-24 hours after ovulation for oocytes, 24-48 in female tract for sperm

Question 10

what aids movement of sperm and eggs?

Answer 10

oocyte moves down oviduct via muscular contractions and beating cilia, cilia help movement of sperm and oocyte and cumulus release chemoattractants to aid sperm

Question 11

stages of acrosome reaction

Answer 11

1 sperm makes contact with egg
2 acrosome swells and makes contact with zona pellucida
3 acrosome reacts with pervitellene space, acrosome releases hydraluronase and exposure of acrosin
4plasma membranes of sperm and egg fuse
5 sperm nucleus enters the egg
6 cortical granules fuse with egg PM which renders perivitelline space impenetrable to sperm

Question 12

what is ZP2 for?

Answer 12

contains sperm binding domain necessary for oocyte sperm recognition. responsible for block to polyspermy

Question 13

what binds on primary gamete binding?

Answer 13

sperm membrane binds zona pellucida via ZP3 and ZP4 on zona

Question 14

what binds on secondary binding?

Answer 14

sperm acrosomal inner membrane binds zona pellucida via ZP2 and acrosin on sperm

Question 15

what does acrosin digest?

Answer 15

zona pelucida and oocyte PM

Question 16

how does sperm/oocyte fusion cause oocyte activation?

Answer 16

PLC released and hydrolyses PIp2 to DAG and IP3, triggering calcium release from intracellular stores and leads to cortical granule release

Question 17

what does DAG activate?

Answer 17

PKC which stimulate phosphorylation of other proteins essential for development of conceptus

Question 18

what resumes after oocyte activation?

Answer 18

meiosis

Question 19

what is cleaved to stop polyspermy?

Answer 19

ZP2

Question 20

what does ovastacin released from cortical granules do?

Answer 20

hardens zona pellucida and inactivates ZP2

Question 21

what is the combination of the sperm and oocyte genomes called?

Answer 21

syngamy