Fertilization

Question 1

At 20 weeks’ gestation, women have about ___________ oocytes. The half-life of these is about _________.

Answer 1

6-8 million; 10 years

Question 2

Oocytes are suspended in __________ for about 45 years.

Answer 2

prophase I

Question 3

The _____________ allows sperm to break through the zona pellucida.

Answer 3

acrosomal reaction

Question 4

What are some problems with blastocyst sampling?

Answer 4

Blastocysts may be mosaic

Embryos undergo editing

Question 5

What is a less invasive way to investigate embryos?

Answer 5

Most aneuploidies arise from the mother. Some labs have started analyzing the discarded polar bodies; if polar bodies have chromosomal abnormalities then it’s likely that the embryo does, too.

Question 6

Give the WHO’s normal range for semen analysis.

Answer 6

• Volume greater than 1.5 mL
• Concentration greater than 15 x 10^6 / mL
• Motility greater than 32%
• Morphology at least 4% normal

Question 7

When should hormone levels be measured in a woman to evaluate for infertility?

Answer 7

Just after menstruation, in the early follicular phase

FSH and E2 are the indicators.

Question 8

What molecule helps keep chromatin condensed?

Answer 8

Protamine - a specialized basic histone with disulfide bonds

Question 9

Sperm binding to the zona pellucida is mediated by _____________.

Answer 9

ZP3

Question 10

Fusion of the sperm membrane with the oocyte membrane causes the release of ______________.

Answer 10

hyaluronidase and acrosin

Question 11

FSH used to be examined to determine the functional health of the ovaries and follicles, but __________ is a better indicator and is now used.

Answer 11

AMH

Question 12

Describe the overall chemistry of the acrosome reaction.

Answer 12

Binding to the oocyte leads to activation of a Gq receptor that leads to sustained calcium entry.

Question 13

______________ is responsible for sperm-oocyte fusion.

Answer 13

Fertilin

Question 14

What cell counts occur in the first week after fertilization?

Answer 14

• One day: two cells

* Three days: four cells

Question 15

what is the zona pellucida?

Answer 15

surrounds the oocyte, a glycoprotein sheet (ZP1-3) made of 70% protein, 20% hexose, 3% sialic acid, and 2% sulphate

Question 16

describe sperm capacitation

Answer 16

• occurs in the female genital tract or the a cAMP medium for in vitro
• causes destabalization of the acrosomal cap, hypermobility of the tail, probably loss of the glycoprotein coat on the sperm head to expose receptor sites

Question 17

describe the cortical reaction

Answer 17

when the sperm binds to the egg plasma membrane, the cortical granules containing hydrolytic enzymes are secreted into the ZP, this causes cleaved ZP2 and a modified ZP3 which makes it so that no other sperm may bind

Question 18

describe male pronuclei formation

Answer 18

the protamines keep sperm chromatin tightly packed with disulphide bonds. these disulphide bonds are reduced by oocyte derived glutathione. this causes sperm nuclei decondensation and the formation of the pronuclei