Fertilisation

Question 1

What is capacitation?

Answer 1

Activates sperm to swim

Question 2

Process of capacitation

Answer 2

Glycoprotein coat acquired in epididymis removed by proteases in cervical fluid

Question 3

How does capacitation work?

Answer 3

Causes cell membrane to become more permeable to calcium ions which activates strong tail lashing/ makes acrosome reaction possible

Question 4

What is the acrosome reaction?

Answer 4

Acrosome fuses with and digests the plasma membrane of the zona pellucida of the egg to release contents

Question 5

What occurs as a result of fusion?

Answer 5

Waves of calcium ions that repeat continuously

Question 6

What is the first effect of calcium waves?

Answer 6

Cortical granules are released which alter the zona pellucida to become impenetrable by sperm/ block further fusion

Question 7

What is the second effect of calcium waves?

Answer 7

Meiosis of the oocyte resumes, second polar body expelled, chromosomes condense and form male and female pronuclei

Question 8

Reasons for assisted fertilisation

Answer 8

Blocked/ absent oviducts (such as sexual transmitted diseases)
Blocked vasa deferentia/ efferentia, impotence, low male fertility
Female age

Question 9

What are the stages of assisted fertilisation?

Answer 9

1. Superovulation (FSH/ block oestrogen detection)
2. Oocyte harvesting
3. Sperm harvesting
4. Capacitation
5. Mix
6. Observation of early development/ genetic testing
7. Embryo transfer

Question 10

What is ICSI?

Answer 10

Intra-Cytoplasmic Sperm Injection, injecting nucleus of sperm

Question 11

How are genes unlike engineering blueprints?

Answer 11

Physical structure no relation to body structure/ genes part of the body/ no external builders/ few opportunities for bringing in inside information/ has to function well enough for each stage

Question 12

What is cleavage?

Answer 12

Mitosis with no growth- remains inside the zona pellucida

Question 13

What occurs at the 4 cell stage?

Answer 13

1. mRNA synthesis from embryo’s own DNA

2. Maternal mRNA destroyed at increasing rate

Question 14

How are different cells made from the morula?

Answer 14

Outside cells with free surface= epithelial/ trophoblast
therefore will become placenta
Fluid pumped inwards
Inside cells with contact/ inner cell mass
Forms blastocyst

Question 15

What happens to the blastocyst?

Answer 15

Hatches through zona pellucida as zygote, produces hCG hormone= LH therefore stops menstrual cycle, signal to mother

Question 16

Where does implantation occur?

Answer 16

Blastocyst travels down fallopian tube, trophoblast of hatched blastocyst invades uterine epithelium to develop into placenta