Fertilization

Question 1

Describe the DNA in sperm (2)

Answer 1

• Haploid
• Highly condensed due to protamines (specialized histones that link to each other using disulfide bonds)

Question 2

What is the sperm’s flagella made of?

What protein helps it move?

Answer 2

Flagella = microtubules

Move due to dynein

Question 3

Oocytes are arrested in _____ I until _______

Oocytes are arrested in ______ II until _______

Answer 3

Oocytes are arrested in Prophase I until ovulation

Oocytes are arrested in Metaphase II until fertilization

*prophase until puberty, metaphase until meet a sperm

Question 4

The zona pellucida is a __________ coat around the egg, made by __________

Answer 4

The zona pellucida is a glycoprotein coat around the egg, made by the oocyte and granulosa cells

Question 5

Name the 4 events of fertilization

Answer 5

1. Sperm binds to zona pellucida’s ZP3 receptor
2. ZP3 binding triggers acrosomal reaction, and sperm digests the zona pellucida
3. Sperm penetrates through zona pellucida
4. Sperm and egg membranes fuse

Question 6

Define sperm capacitation

Answer 6

Final step in which sperm gain ability to perform acrosomal reaction and fertilize the egg

Question 7

Where does capacitation occur?

What are its 2 major parts?

Answer 7

Occurs in female reproductive tract

(1) Flagella becomes hyper motile
(2) acrosomal cap gets destabilized

Question 8

Sperm bind to ____ on the zona pellucida

Answer 8

Sperm bind to ZP3 on zona pellucida

Question 9

How does the egg prevent polyspermy?

Answer 9

• Once egg begins Meiosis II, it releases cortical granules
• These granules change the zona pellucida to prevent additional sperm from penetrating

Question 10

What causes the sperm DNA to de-condense?

Answer 10

Glutathione from oocyte reduces the disulfide bonds holding sperm protamines together

Question 11

When does the embryo first gain polarity?

Answer 11

Day 5

(when it becomes a blastocyst)

Question 12

What are the 3 measures of semen quality?

Answer 12

Concentration

Motility

Morphology

Question 13

How do we determine a woman’s egg supply? (4)

Answer 13

• Measure FSH, E2, AMH
• Ultrasound

Question 14

Where does fertilization occur most commonly?

Answer 14

Ampulla of fallopian tube

Question 15

What is the difference between gestational and embryonic age?

Answer 15

• Gestational: calculated from date of last period
• Embryonic: calculated from date of conception

*2 weeks different

Question 16

Implantation occurs within ___ days of fertilization

Answer 16

Implantation occurs within 6 days of fertilization