Lecture 09: Fertilization (Pozor)

Question 0

definition of fertilization

Answer 0

the process by which the male and female gametes unite to form a single celled zygote

Question 1

sequence of events of sperm/oocyte interaction

Answer 1

1. occyte maturation to 2nd meiotic division, ovulation
2. sperm - capacitation, acrosome reaction
3. penetration of cumulus and zona pellucida
4. ionic changes, cortical granules release - block to polyspermy
5. meiotic resumption, 2nd polar body extruded
6. pronuclear formation
7. DNA synthesis
8. metabolic exchange
9. syngamy - merging haploid sets of chromsomes on mitotic spindle
10. cleavage

Question 2

what is the ovulated oocyte surrounded by?

Answer 2

• cumulus oophorus
• zona pellucida (Z1, Z3, Z3)
• perivitelline space with first polar body
• viteline membrane

Question 3

what is special about ZP3?

Answer 3

it will bind with receptors on membrane of sperm cell. without ZP3 there is no fertilization because sperm would not be able to penetrate through zona pellucida

Question 4

zona pellucida glycoprotein 3 (ZP3)

Answer 4

a sperm receptor which binds zona binding receptor (ZBR) on newly exposed sperm head. Activates acrosome reaction promoting region (ARPR)

Question 5

activation of ARPR causes what reaction to occur?

Answer 5

acrosome reaction

Question 7

what do sperm do? what is their schtick? (they do 4 main things)

Answer 7

1. maturation in the epididymis
2. ejaculation
3. capacitation
4. acrosome reaction

Question 8

what is capacitation?

Answer 8

no change in sperm morphology it’s just a motility change. a hyperactivation. they use more cAMP and increase power output

Question 9

where does capacitation occur?

Answer 9

in the female repro tract, mostly in the isthmus of the oviduct

Question 10

what causes capacitation to occur?

Answer 10

1. an increase in pH
2. changes in intracellular Ca
3. changes in the tail - hyperactivation

Question 11

what is necessary for activation of the membrane signal transduction pathways of capacitation?

Answer 11

transfer of cholesterol to albumin

Question 12

what is necessary for phosphorylation of proteins and polymerization of actin throughout capacitation?

Answer 12

activation of protein kinase A

Question 13

what is necessary for hyperactive sperm motility in capacitation?

Answer 13

tyrosine phosphorylation of proteins

Question 14

what is necessary for sperm penetration into the oocyte and decondensation of sperm DNA?

Answer 14

polymerizationof globular actin to filamentous actin

Question 15

acrosome reaction

Answer 15

1) Fusion of the sperm plasma membrane with the outer acrosomal membrane
2) Desquamation (destroying) of sperm’s outer membrane (inner membrane still intact)
3) enzymes spilled out of sperm cell which break down egg’s coating and allow fertilization to take place

Question 16

hydrolytic enzymes released during acrosome reaction

Answer 16

hyluronidase, acrosin

Question 17

What is my Bella’s favorite word?

Answer 17

YESHHH

Question 18

ZP2

Answer 18

sperm binds to it in secondary binding in zona pellucida after acrosomal reaction takes place. Helps to actively pull sperm into the oocyte

Question 19

zona block

Answer 19

mechanisms within zona pellucida to block polyspermy:

1) cortical granules exocytosis and hardening of zona pellucida
2) modification of ZP3 and ZP2

Question 20

Membrane (vitelline) block

Answer 20

changes in vitelline membrane polarization to block polyspermy

Question 21

What hormone inhibits further meiosis after second arrest in metaphase II? ***

Answer 21

Maturation Promoting Factor (MPF)

Question 22

What inhibits MPF and allows meiosis to resume after second arrest?

Answer 22

sudden influx of Ca

Question 23

What must occur when sperm enters oocyte before fusion of DNA can occur?

Answer 23

decondensation of DNA into male and female pronuclei

Question 24

syngamy

Answer 24

fusion of male and female pronuclei in fertilization. Forms zygote