Fertilisation

Question 1

Polyspermic zygotes are

Answer 1

Polyploid

Have multiple centrioles
Cleave abberantly at the first division
Leads to embryonic death

Question 2

Pronuclear migration

Answer 2

Overtime the sperm and egg pronuclei move closer together until they fuse

Question 3

Blastomeres

Answer 3

Many small nucleated cells produced from mitotic divisions during cleavage

Question 4

The acrosomal process

Example

Answer 4

In some species
A region of globular actin
Between the acrosome and the nucleus

Sea urchins: actin in sperm head elongates to form acrosomal process that pushes the acrosomal vesicle forward to empty it

Question 5

Haploid nuclei contain

Answer 5

Highly compacted DNA

Question 6

The centriole

Answer 6

Lies just behind the nucleus and will form one of the two spindle poles in the first division

Question 7

Vitelline membrane

Answer 7

Thin glucoprotein meshwork surrounding the egg membrane

Often involved in sperm egg recognition

Question 8

Jelly layer

Answer 8

A second glycoprotein meshwork surrounding the egg that attracts or activates sperm

Question 9

Egg cytoplasm

Answer 9

Rich in proteins (yolk), ribosomes, RNA and other components required for embryogenesis

Question 10

Egg cortex is

Answer 10

A specialises part of cytoplasm that lays just below the egg membrane containing cortical granules

Question 11

Bindin

Answer 11

Sea urchin protein
Coats inner membrane of acrosomal vesicle and the outside of the acrosomal process
Species specific
React with receptors on surface of the egg that mediate interaction between sperm and egg membranes
Bindin receptors are limiting: restrict number of sperm that can bind and interact with egg membrane