Fertilization

Question 1

Fertilization is?

Answer 1

when the sperm enters the egg and a zygote is formed in order to propel the 1st stages of development

a complex sequence of chemical cascades

Question 2

Major steps in fertilization (4)

Answer 2

1. Contact and recognition
2. Regulation
3. Fusion of male and female genetic material
4. Activation

Question 3

Sperm Cell Structure

Answer 3

• Acrosome
• Nucleus
• G-actin
• Centriole
• Axoneme
• Mitochondria

Question 4

Acrosome

Answer 4

1. Contains enzymes that can digest proteins and the egg jelly
2. Bindin protein - adhesion of the sperm acrosomal process to the vitelline layer

Question 5

Nucleus

Answer 5

Haploid - contains 1/2 of the genetic material needed for fertilization

Question 6

G-actin

Answer 6

Globular actin - in b/w the acrosome and the nucleus, can polymerize and create F-actin microfilaments that can change the cell shape

Question 7

Centriole

Answer 7

MTOC - microtubule organizing center: long polymers of the tubulin proteins

Question 8

Axoneme

Answer 8

Structure formed by microtubules connected to the centriole; major portion of the flagellum

Question 9

Egg Cell Structure

Answer 9

• Egg Cortex
• Cortical Vesicle
• Vitelline Layer
• Jelly Coat
• Follicular cells
• Egg plasma Membrane

Question 10

Egg Cortex

Answer 10

gel-like, stiffer, contains lots of g-actin f-actin

Question 11

Cortical Vesicle

Answer 11

membrane bound vesicles inside the egg cortex

contains:

1. Glycosaminoglycans (GAGs)
2. Enzymes
3. can help hold cells together

Question 12

Vitelline Layer

Answer 12

Fibrous mat close to the egg plasma membrane. Contains bindin receptors

Question 13

Jelly Coat

Answer 13

Made of GAGs and glyco-proteins, triggers acrosomal rxn in sperm. Can attract sperm / activate sperm

Question 14

The Cytoplasmic trove includes

Answer 14

• Nutritive proteins
• Ribosomes & tRNA
• mRNA
• Morphogenetic factors
• Protective Chemicals

Question 15

Nutritive proteins

Answer 15

supply of energy and amino acids

Question 16

Ribosomes & tRNA

Answer 16

accomplishes protein synthesis

Question 17

mRNA

Answer 17

accumulates proteins then encodes proteins for the early stages of development

Question 18

Transcription factors

Answer 18

bind to chromosomes

get into the nucleus of the developing embryo to turn genes on/off

Question 19

para crine factors

Answer 19

released to the outside of the cell to affect the behavior of neighboring cells

Question 20

Sperm Mobility

Answer 20

Sperm become active in sea water due to the change in pH that activates Dynein.
Sperm finds the eggs through chemotaxis, direction is provided by resact

Question 21

Acrosome Reaction

Answer 21

When the sperm membrane comes into contact with the egg jelly:

1. Ca++ channels open and calcium ions from SW rush into the sperm
2. Sodium/Hydrogen exchange pump opens –> pH rises in the sperm head
3. Rise in IP3 –> release of Ca++

Question 22

Exocytosis

Answer 22

Triggered by the rise in Ca++
A membrane bound vesicle fusing with the plasma membrane to release its contents leading to actin polymerization (g-actin to f-actin)

Question 23

Egg Response

Answer 23

1. Na+ influx
2. Change in egg cell electrical potential
3. Electrical “shiver” = Fast Block to polyspermy

Question 24

Fertilization Envelope

Answer 24

Modified vitelline layer, separated from the surface of the egg, no bindin receptors, Slow Block