Fertilization

Question 1

What are the important cytoplasmic contents of an egg cell?

Answer 1

Yolk proteins
Ribosomes and tRNAs
Determinants
Proteins and mRNAs
Protective chemicals

Question 2

What is an egg cell called before ovulaltion?

Answer 2

Oocyte

Question 3

What is an egg cell called after ovulation?

Answer 3

Ovum

Question 4

What is an egg cell called after fertilization?

Answer 4

Zygote

Question 5

What are the two outcomes of fertilization?

Answer 5

1. Combines genes from parents- sexual reproduction
2. Initiates the development of a new multicellular organism

Question 6

How does the sperm find the egg for fertilization to occur?

Answer 6

Chemotaxis

Question 7

What happens in chemotaxis in relation to fertilization?

Answer 7

-The egg releases peptides which diffuse to form a concentration gradient
-The sperm have receptors and will move to areas of higher concentration
-The binding of calcium causes the sperm to swim faster towards the higher concentration

Question 8

Why is peptide binding during fertilization important

Answer 8

This is the first level of species specificity
-this ensures genetic compatibility

Question 9

How does a sperm cell enter and egg cell?

Answer 9

-The sperm contacts the jelly layer which triggers the acrosome reaction
-The acrosome vesicle opens to release enzymes to digest the jelly coat
-An acrosome processing tube grows and attaches to the vitelline membrane of the egg cell
-Bindin is released from the process and binds to receptors on the egg cell
-The egg and sperm membranes fuse

Question 10

Is the acrosome reaction the second level of species specificity?

Answer 10

Yes
-every time receptors are involved it is a layer of species specificity

Question 11

Is the use of bindin to fuse the membranes the last level of species specificity?

Answer 11

Yes

Question 12

How do we solve the issue of polyspermy (multiple sperm binding to one egg cell)?

Answer 12

1. Fast block
2. Slow block

Question 13

What is the fast block method to avoid polyspermy?

Answer 13

-When the sperm bind to the vitelline membrane of the egg, membrane potential changes
-Na+ comes into the cell from the water so the membrane potential is now POSITIVE
- THIS OCCURS ONLY IN SEA URCHINES

Question 14

What is the slow block method to avoid polyspermy?

Answer 14

-After the sperm binds to the vitelline membrane, cortical granules excyst
-Granules release the following between the egg and the vitelline membrane
-Protease
-Mucopolysaccharides
-Peroxidase
-Hyalin proteins

Question 15

What happens when the granules are released to prevent polyspermy?

Answer 15

-Protease: remove bindin receptors with sperm attached and cleaves the membrane between the egg and the vitelline membrane so egg can leave
-Mucopolysaccharide: pulls in water to elevate the vitelline membrane
-Peroxidase: kills any sperm that have penetrated the vitelline
-Hyalin Proteins: form a protective coating around the egg