Week 2 Objective Explain the role of ZP3 on the Zona Pellucida

Question 1

Penetrating the Corona Radiata

4 things, in order

Answer 1

Fusion of the outer acrosomal membrane with the sperm plasma membrane creates a portal through which the contents of the acrosome can be released

Fragmentation of the plasma membrane & acrosomal membrane leads to release of acrosomal enzymes

Hyaluronidase is one of the major enzymes in the acrosome, breaks down hyaluronic acid in the ECM of the cells of the corona radiata

swimming movement of spermatazoa helps in the penetration

Question 2

ZP3

Answer 2

one of the four glycoproteins in the zona pellucida

mediates the attachment of the sperm to the ZP

stimulates acrosomal reaction in mammals

massive influx of calcium through sperm plasma membrane

exchange of sodium (influx) and hydrogen (efflux)

followed by penetration of the sperm through zona pellucida

Question 3

Acrosin

Answer 3

most important enzyme in the penetration of zona pellucida (called zona lysin in the past)

is not “released”: remains attached to the portion of acromsomal membrane that is attached to the plasmalemma

digests a hole through the ZP and assists the swmming portion of the spermatazoa through ZP

Question 4

After full penetration and fusion of the sperm to the egg, what occurs

Answer 4

the sperm releases mitochondria, centrioles, and nucleus

flagellum is external to the oocyte

Question 5

Blocks to polyspermy

Answer 5

fast block: depolarization of oocyte prevents further penetration of oocyte and gives it time to set up the slow block

slow block: release of polysaccharides into the perivitelline space–between zona pellucida and plasmalemma; hydrates space and increases inner space

Question 6

Metabolic activation of the egg

Answer 6

initiated by release of calcium ion within egg cytoplasm in response to phosopholipase C zeta by sperm

Question 7

phospholipase C zeta

Answer 7

released by sperm and initiates influx of calcium into egg cytoplasm

released calcium initiates blocks to polyspermy

stimulates increase in egg respiration and metabolism via Na/H ion exchange mechanism

results in an increase in pH and an increase in oxidative metabolism

Question 8

Decondensation of sperm nucleus

Answer 8

tight pack of sperm DNA is due to SS cross linking among protamine molecules

sperm nuclear membrane becomes more permeable and allows entry of egg cytoplasmic factors to reduce disulfide cross linkage of sulfhydryl groups

tightly packed sperm chromatin becomes more loosely packed and male pronucleus established

Question 9

pronucleus occurs when

Answer 9

cytoplasmic factors from oocyte cytoplasm break down the sulfydryl bonds making sperm chromatin so tight

Question 10

put these in order

a. decondensation of sperm nucleus
b. organization of first mitotic spindle by sperm centrosome
c. completion of meiosis in oocyte

Answer 10

a, c, b

Question 11

Pronuclei

Answer 11

the nuclear material from a sperm or oocyte after the eggs has been penetrated by the spermatazoan

male pronucleus = decondensed nuclear material
female pronucleus = chromosomal material surrounded by a pronuclear membrane derived from the endoplasmic reticulum

Question 12

zygote =

Answer 12

a single celled stage when male/female pronuclei have fused and share a common membrane, must be 2n

Question 13

in vitro fertilization process

Answer 13

removal of eggs through laparascopy

combined with sperm sample

in vitro fertilization

early cleavage in vitro

extra embryos frozen

reimplantation into uterus, up to 3 embryos