Lecture 09: Fertilization (Pozor) Flashcards Preview

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Flashcards in Lecture 09: Fertilization (Pozor) Deck (24):
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sequence of events of sperm/oocyte interaction

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

1

definition of fertilization

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

2

what is the ovulated oocyte surrounded by?

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

3

what is special about ZP3?

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

4

zona pellucida glycoprotein 3 (ZP3)

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

5

activation of ARPR causes what reaction to occur?

acrosome reaction

7

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

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

8

what is capacitation?

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

9

where does capacitation occur?

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

10

what causes capacitation to occur?

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

11

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

transfer of cholesterol to albumin

12

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

activation of protein kinase A

13

what is necessary for hyperactive sperm motility in capacitation?

tyrosine phosphorylation of proteins

14

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

polymerizationof globular actin to filamentous actin

15

acrosome reaction

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

16

hydrolytic enzymes released during acrosome reaction

hyluronidase, acrosin

17

What is my Bella's favorite word?

YESHHH

18

ZP2

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

19

zona block

mechanisms within zona pellucida to block polyspermy:
1) cortical granules exocytosis and hardening of zona pellucida
2) modification of ZP3 and ZP2

20

Membrane (vitelline) block

changes in vitelline membrane polarization to block polyspermy

21

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

Maturation Promoting Factor (MPF)

22

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

sudden influx of Ca

23

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

decondensation of DNA into male and female pronuclei

24

syngamy

fusion of male and female pronuclei in fertilization. Forms zygote

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