fertilization

Question 1

describe the sperm head structure

Answer 1

head: 3-5um length, 2-3um width. Highly condensed chromatin in nucleus, acrosome (double layered membrane sac containing hydrolytic enzymes)

Question 2

what are protamines

Answer 2

a specialized histone that tightly wraps DNA by disulfide bonds and keeps the crhomatin condensed

Question 3

Sperm tail structure

Answer 3

contains 9 axoneme doublets arranged circumferentially around a pair of microtubules. These doublets, in turn, are surrounded by a mitochondrial sheath. The tail is responsible for sperm motility via dynein regulation

Question 4

describe oocyte meiosis

Answer 4

Primary oocytes arrest at prophase I. Following completion of meiosis I, a secondary oocyte and first polar body are generatd. After fertilization, the oocytes will resume meiosis and generate the second polar body.

Question 5

what does semen analysis look for

Answer 5

Volume (>2ml), sperm concentration (>20 million/ml), motility (>50% motile), morphology (14% nl), rate of forward progression (>50% nl).

Question 6

Describe sperm capacitation

Answer 6

The process by which spermatozoa acquire the capacity to undergo the acrosome reaction and fertilize eggs. Following capacitation, sperm display an increase in the frequency and amplitude of the flagellar beat of the tail and are able to bind to the zona pellucida surrounding the egg.

Question 7

List the steps of sperm-egg interaction leading to fertilization

Answer 7

sperm bind to the zona pellucida (ZP) > the acrosome reaction > ZP penetration > oolemma fusion > intravitelline processing

Question 8

Zona pellucida structure

Answer 8

Shell-like structure that surrounds oocytes. Contains three glycoproteins- ZP1, ZP2 and ZP3.

Question 9

Sperm binding to zona pellucida is mediated by…

Answer 9

ZP3

Question 10

describe acrosome rxn

Answer 10

The outer membrane of acrosome fuses with the plasma membrane of sperm resulting in the release of hyaluronidase and acrosin. These enzymes allow for fusion of the sperm with the oocyte.

Question 11

Fusion of sperm-oocyte

Answer 11

Requires fertilin, a sperm protein. Fusion occurs btw the sperm’s plasma membrane and the oolemma.

Question 12

Oocyte activation

Answer 12

•The reawakening of the oocyte in regards to second meiotic division. Morphological indicator: exocytosis of cortical granules

Question 13

Zona reaction

Answer 13

aka cortical rxn. The oocyte releases cortical granules and forms new glycoprotein ZP3-F which is no longer capable of binding sperm. This prevents more than one sperm from fertilizing the egg (polyspermy)

Question 14

Formation of male pronuclei

Answer 14

. Up to this point, the chromatin within the mature sperm nucleus was kept tightly packed with disulfide bonds. These disulfide bonds are reduced by the action of oocyte-derived glutathione, and the sperm nucleus decondenses.