Making embryos

Question 1

What are the three steps of fertilization?

Answer 1

Penetration through the cumulus cell matrix
Penetration through the zona pellucida
Fusion with the egg plasma membrane

Question 2

How is the cumulus cell matrix tightly bound?

Answer 2

Cell adhesion proteins and hyaluronic acid

Question 3

What triggers the release of EGF receptor ligands by mural granulosa cells?

Answer 3

LH

Question 4

How is hyaluronic acid released?

Answer 4

Pro-factors and ligands upregulate the transcription of genes

Question 5

What is the role of sperm-specific hyaluronidases?

Answer 5

They surround the surface of the sperm and digest the hyaluronic acid, allowing the sperm to get through the matrix

Question 6

How many proteins are found in the zona pellucida in primates?

Answer 6

Four

Question 7

Deletion of which zp proteins prevents assembly of zona?

Answer 7

zp2 and zp3

Question 8

What test can be done to observe the role of zp2 in fertilization?

Answer 8

Replace mouse zp gene by human homologue; mix transgenic mouse egg with human sperm -> sperm doesn’t stick to the zona of mouse egg BUT sticks to zp2 of human egg

Question 9

What sperm membrane protein is required for sperm-egg fusion?

Answer 9

Izumo

Question 10

Izumo gene activation leads to _____________ males and _____________ females

Answer 10

Infertile; fertile

Question 11

True or false: Izumo knockout leads to the inability for sperm to stick to the membrane

Answer 11

False, it disables sperm from fusing into the membrane while still being able to stick to the membrane

Question 12

What egg membrane protein is required for sperm-egg fusion?

Answer 12

Juno

Question 13

Juno binds to ___________

Answer 13

Izumo

Question 14

Fluorescent Izumo no longer binds to __________ because anti-_____________ antibody covers ____________

Answer 14

Juno; Juno; Juno

Question 15

Deleting Juno from males led to no _____________ and deleting Juno from females led to no _______________

Answer 15

Effect; fertilization

Question 16

What is another membrane protein required for sperm-egg fusion?

Answer 16

CD9

Question 17

CD9 is a member of ________________ cell surface protein family

Answer 17

Tetraspanin

Question 18

CD9 gene inactivation leads to ____________ males and severely sub-fertile _______________

Answer 18

Fertile; females

Question 19

What is the role of CD9 in fertilization?

Answer 19

CD9 aggregates Juno proteins on the cell surface for easier targeting of Izumo on the sperm

Question 20

Which of the following is part of the activation of the egg?
a) Initiation of mitotic cell cycles of embryo
b) Completion of the first meiotic division

Answer 20

a)

Question 21

How is the increase of intracellular calcium linked to the mechanism of activation?

Answer 21

Sperm penetration induces repetitive release of calcium ions
Parthenogenetic stimuli induce calcium release
Inhibiting release of calcium prevents activation of the egg

Question 22

How does the sperm trigger calcium release in the egg?

Answer 22

Sperm acts as a ligand to activate intracellular signaling pathway
Sperm component enters oocyte cytoplasm, triggers calcium release

Question 23

How are G-protein coupled receptors and phospholipase C linked to calcium release?

Answer 23

G-protein binds to GPCR and triggers phospholipase C to break down PIP3 into IP3 and diacylglycerol
IP3 triggers the calcium release

Question 24

True or false: Sperm specific phospholipase C is required for release in the egg

Answer 24

True

Question 25

Is sperm release linked to GPCR?

Answer 25

No, sperm releases its own phospholipase C

Question 26

Where can polyspermic fertilization be blocked?

Answer 26

Zona pellucida and membrane of egg

Question 27

Calcium released at fertilization triggers cortical granule _______________

Answer 27

Exocytosis

Question 28

Cortical granules are responsible for modifying _________ so that sperm can no longer bind to the zona

Answer 28

zp2

Question 29

What protein cleaves zp2 at the disulfide bonds and modifies the zona pellucida?

Answer 29

Ovastacin

Question 30

When does meiosis II occur in the egg?

Answer 30

After fertilization

Question 31

How many polar bodies are formed after fertilization?

Answer 31

Two

Question 32

At which phases of meiosis is cohesin degraded?

Answer 32

Anaphase I and II

Question 33

How is separase activated?

Answer 33

CDC20 and APC form a complex that activates separase by separating it from securin

Question 34

What inhibits the CDC20/APC complex in the first meiotic division?

Answer 34

Spindle assembly checkpoint

Question 35

What inhibits the CDC20/APC complex in the second meiotic division?

Answer 35

EMI2

Question 36

What causes the degradation of EMI2?

Answer 36

Calcium

Question 37

During the first period of DNA replication, chromosomes from egg and sperm are _____________ in the oocyte

Answer 37

Separate

Question 38

Histones replace ______________ in sperm chromatin __________ fertilization

Answer 38

Protamines; after

Question 39

The period of development before implantation into the uterus lasts _______ days

Answer 39

Five

Question 40

Cleavage divisions produce an embryo containing ____________ cells

Answer 40

50-100

Question 41

What is morula?

Answer 41

Cells are flattened against each other to increase surface area

Question 42

When does activation of embryonic transcription occur in humans and in mouse?

Answer 42

Major activation occurs at 2-cell stage in mouse, 4-cell stage in humans

Question 43

Which cells form the blastocyst?

Answer 43

Epiblast (primitive ectoderm) and primitive endoderm (inner cell mass) + trophectoderm

Question 44

The primitive ectoderm gives rise to which cell types?

Answer 44

All tissues of the embryo, amnion, allantois, yolk sac mesoderm

Question 45

The primitive endoderm gives rise to which cell type?

Answer 45

Yolk sac endoderm

Question 46

The trophectoderm gives rise to which cell type?

Answer 46

Fetal portion of placenta

Question 47

What are the two models that determine the fate of inner and outer cells?

Answer 47

Inside-outside model where fate is determined by position Polarity model where differential inheritance of polarity domains determine cell fate

Question 48

What is the Hippo signaling pathway?

Answer 48

Mob1 and LATS1/2 is activated when MST1/2 and SAV1 are phosphorylated and ubiquitinates YAP/TAZ complex for degradation

Question 49

When the hippo signaling pathway is off, the YAP/TAZ complex is ______________

Answer 49

Activated

Question 50

If Hippo is off and YAP is stabilized, which cell type is formed?

Answer 50

Trophectoderm

Question 51

If Hippo is on and YAP is degraded, which cell type is formed?

Answer 51

Inner cell mass

Question 52

AMOT cannot recruit the machinery that phosphorylates YAP in the _____________ domain

Answer 52

Apical

Question 53

AMOT can recruit the machinery that phosphorylates YAP in the _________________ domain

Answer 53

Basolateral

Question 54

FGF signaling differentiates primitive ectoderm and primitive ______________

Answer 54

Endoderm

Question 55

The epiblast expresses ___________ while the primitive endoderm expresses ________________

Answer 55

Nanog; Gata6

Question 56

Why is X-chromosome inactivated?

Answer 56

To equalize the gene dosage

Question 57

One X-chr becomes inactivated in _________ and a single X-chr remains active in ____________

Answer 57

Females; males

Question 58

What is the mechanism of X-chr inactivation?

Answer 58

Xist RNA is expressed from one X-chromosome Xist RNA coats that X-chr Xist-coated X is transcriptionally inactive

Question 59

When does X-chr inactivation occur?

Answer 59

After implantation

Question 60

Some genes are ___________ and escape inactivation

Answer 60

Conserved