Fertilization

Question 1

Protamines

Answer 1

found in sperm head

Specialized basic histone tightly held together by disulfide bond cross-linking

Question 2

Axial filament of sperm tail

Answer 2

9+2 array of microtubules typical of cilia and flagella

• kartageners ciliary defect
• tx for infertility: inject non-motile sperm into egg

Question 3

In order to deposit sperm we need what 3 things?

Answer 3

1. Sufficient number
2. Motility
3. Morphology

Question 4

[ ] of semen should be? How many of that needs to be motile?

How many need to look normal (morphology)?

Answer 4

Ejaculate volume: 2 ml

Sperm [ ]:
>20x106/ml (20 mill)

Sperm motility: > 50% need to be motile

Morphology:
14% nl

Question 5

Sperm capacitation

Answer 5

process where spermatozoa acquires the capacity to undergo the acrosome rxn and fertilize eggs
(bind to ZP and undergo acrosomal rxn)
- process occurs in female genital tract

Question 6

Sperm egg intxn

Answer 6

1. SPerm activated by female reproductive tract
2. SPerm binds zona pellucida
3. Acrosomal rxn
4. Sperm lyses hole in zona and penetrates
5. Sperm and egg membrane fuse (oolemma fusion)
6. Intravitelline processing

Question 7

Zona pellucida

Answer 7

Shell like structure that surrounds oocyte

• glycoprotein sheet with several microns thick
  1. ZP1
  2. ZP2
  3. ZP3
• sperm binding to zona is mediated by ZP3

Question 8

• sperm binding to zona is mediated by ___

Answer 8

ZP3

Question 9

Acrosomal rxn:
When outer membrane of the acrosome fuses with the plasma membrane of the sperm, it exposes what? What is the protein responsible for sperm-oocyte fusion?

Answer 9

the contents of the acrosome (hyaluronidase and acrosin)
- Involves G prot VGCC

Fertilin: responsible for sperm-oocyte fusion

Question 10

2nd meiotic division happens when?

Answer 10

oolemma is penetrated

Question 11

Sperm head has a very highly condensed chromatin in the nucleus, what molecule is responsible for keeping it condensed?

Answer 11

Protamine
- a specialized histone that tightly wraps DNA by disulfide bonds

*these bonds are reduced by the action of oocyte-derived glutathione and the sperm nucleus decondenses

Question 12

What rxn prevents more sperm fertilization? (polyspermy)

Answer 12

The zona rxn:
- egg releases cortical granules (lysosomal enzymes) and forms new glycoprotein ZP3-F
(which is NOT capable of binding sperm like ZP3)

Question 13

Chromatin w/in the mature sperm nucleus was kept tightly packed with disulfide bonds (via protamines), what reduces these bones?

Answer 13

Oocyte activation and completion of meiosis

bonds are reduced by the action of oocyte-derived glutathione and the sperm nucleus decondenses