Repro Exam 3: Fertilization

What is the relative length of time that germ cells are viable?

Mouse- sperm live for 6-12 hr and oocyte lives for 6-15 hr

Pig- sperm live for 25-50 hr and oocyte lives for 8-10 hr

Cattle- sperm live for 30-48 hr and oocyte lives for 8-12 hr

Human- sperm live for 28-48 hr and oocyte lives for 6-24 hr

*Oocyte has shorter lifespan*

What are the important events involved in fertilization?

1. Capacitation

2. Sperm penetrate between cumulus cells

3. Sperm attach to zona pellucida

4. Sperm penetrate zona pellucida

5. Fusion of sperm and oocyte membranes

How many polar bodies are present after fertilization?

2 or 3

True or false: Having 3 polar bodies is normal

True 

How can you get 3 polar bodies?

When fertilization occurs of the 1st polar body, it can also split into 2 making 3 total

True or false: After sperm enter the perivitelline space, the sperm embed into cillia?

False; it embeds into microvilli 

What are the characteristics of the cumulus cells in the cumulus-oocyte complex?

Embedded in extracellular matrix (ECM)

ECM contains hyaluronic acid that helps with sperm penetration

Purpose/characteristics of ZP1, ZP2, and ZP3

ZP1- structural support

ZP2- structural support, helps an acrosome reacted sperm move through zona

ZP3- zona protein that binds to a receptor on the sperm plasma membrane and induces the acrosome reaction

What must be completed before the sperm can fuse to the secondary oocyte with 2 polar bodies?

Acrosome reaction 

How does the acrosome reaction progress?

Occurs when sperm comes in contact with zona pellucida 

1. Perforations develop in acrosome

2. Point fusions of the sperm plasma membrane and external acrosomal membrane occur

Associated with release of acrosome enzymes that facilitate fertilization

What is the difference between supplementary sperm and supernumerary sperm?

Supplementary- extra sperm which pass through the zona pellucida into the PV space (not an issue)

Supernumerary- extra sperm which succeed in entering the vitellus; these ova are said to show polyspermy (are an issue)

What is polyspermy and how is it blocked?

Polyspermy- when more than one sperm manages to enter the ovum

Blocked through the zona reaction or vitelline block

What is slow block vs fast block?

Slow- Zona reaction: modifies the zona pellucida making it impenetrable to other sperm 

Fast- Vitelline block: preventing additional sperm from binding to oocyte plasma membrane 

Which species use which type of polyspermy block?

Zona reaction- cow & pig

Vitelline block- rabbit

Both- rats & mice

What are factors that reduce the effectiveness of the block of polyspermy?

Age of oocyte, high temps, or excessive sperm numbers

What happens after sperm is engulfed?

2nd meiotic division of oocyte is completed

Sperm nucleus decondenses

Formation of male pronucleus

Define/describe syngamy

Membranes of the pronuclei break down, chromosomes condense and arrange themselves for mitotic division  

What are the different types of twins and how they come to be?

Monozygotic (monoovular)- fertilized, single egg that splits into 2 developing zygotes at a very early stage; identical twins, same sex

Dizygotic (polyovular)- fertilization of 2 sperm of 2 separate ova; not identical, can be different sexes; increases with age of mother

What are some examples of how fertilization can go away?

Too many sperm leading to abortion

Infertility

Bad timing