Cleavage

Question 1

A 4-Cell stage has ____ cells while a Morula Stage has ______ cells.

Answer 1

1. Totipotent

2. Pluripotent

Question 2

Dev Embryo Regulation

Answer 2

Ability of Embryo to Compensate for Removal of structures for Addition of Structures

Question 3

Features of a Blastocyst

Answer 3

• Surrounded by ZP
• Large Blastocoel
• Trophoblast w/ Inner cell mass
• Polarized

Question 4

Without Oct-4, ICM would differentiate to what?

Answer 4

TROPHOBLAST

Question 5

For an embryo to be Normal, it must posses both of what?

Answer 5

• Pronucleus from SPERM

- Pronucleus from EGG

Question 6

The Genes involved in differentiation

Answer 6

• Cdx-2
• Oct-4
• Nanog
• Sox2

Question 7

Establishment of Poalrity

Answer 7

• Polarization creates a recognizable APICAL & BASAL Surfaces
• Polarization of Blastomeres determines whether cells are destined to become part of the ICM or Trophoblast

Question 8

What stage is the Zygote considered an Embryo

Answer 8

Blastocyst at the 58-cell stage

Question 9

What happens when the ICM does not properly separate?

Answer 9

• Conjoined twins

Question 10

Mutation of Prader-Willi is ALWAYS inherited from Whom? How?

Answer 10

From Father

• Deletion of LONG arm on Chrom 15

Question 11

Sox2

Answer 11

• Helps to control Regulation of genes involved in differentiation
• Works along with Oct-4

Question 12

Cleavage of a Fertilized egg (Zygote)

Answer 12

1. Zygote
2. 2-cell
3. 4-cell
4. Morula
5. Blastula
6. Gastrula

Question 13

T/F: Potency is Greater than Fate.

Answer 13

True

Question 14

OCT-4

Answer 14

• Expressed in dev Oocytes and Zygotes

- Req for 2-cell cleavage

Question 15

T/F: The Zygote loses the ZP prior to Implantation.

Answer 15

True

Question 16

When is Sox2 first expressed?

Answer 16

8-cell stage

Question 17

X-inactivation takes place when?

Answer 17

During first few weeks of Dev

Question 18

X-inactivation is brought about by what transcript?

Answer 18

Xist

Question 19

When does the maternal gene products stop production in the developing zygote?

Answer 19

Immediately After the 2-Cell stage of development

Question 20

What stage does Polarization take place?

Answer 20

8-16 cell stage

Question 21

Cell Polarity Model

Answer 21

Depends on PLANE of Cell division during cleavage

PARALLEL

Or

PERPENDICULAR

Question 22

Cdx-2

Answer 22

• Essential for Troph cell DIFFERENTIATION

Question 23

Oct-4 is expressed in what type of cells?

Answer 23

All MORULA cells

Question 24

Without Nanog, ICM would differentiate to what?

Answer 24

ENDODERM

Question 25

Prader-Willi Characteristics

Answer 25

- Small Hands and Feet - Short Stature - Poor sexual dev - Mental retardation

Question 26

What happens when the ICM splits in ONE Blastocyst?

Answer 26

- Identical Twins - Formed in one Trophoblast - One sac

Question 27

What is the Stage where the cells do NOT Divide evenly?

Answer 27

Morula Stage

Question 28

Methylation Cycle

Answer 28

- Egg and Sperm Highly methylated - Demethylation of parental genomes occur shortly after Fertilization - Then Remethylation in Late Blastocyst - Methylation fall after genital ridges - Remethylation occurs during late gametogenesis

Question 29

Coating the X-Chrom with Xist causes what?

Answer 29

- Methylation of Histones - Alteration of Histone composition - removal of acetyl groups from histones

Question 30

Hatching

Answer 30

Blastocyst protruding out of the ZP

Question 31

Purpose of X-inactivation

Answer 31

To Provide EQUAL expression of X-Chrom in Both Males and Female

Question 32

Post fertilization Events

Answer 32

The Zygote - Becomes metabolically active - Undergoes cleavage - Transported down Uterine tube to uterus (Several Days) - Implantation

Question 33

Parental Imprinting Characteristics

Answer 33

- Involves the methylation of DNA - Maintained throughout development - ERASED and REESTABLISHED w/ each round of Gametogenesis

Question 34

In terms of Polarity, in Parallel cleavage the Troph will be ____ and the ICM will be ____.

Answer 34

1. Polar | 2. Apolar

Question 35

Inner Cell Mass

Answer 35

- Inner collection of Cells | - Forms Embryo and its structures

Question 36

Parental Imprinting occurs when?

Answer 36

During Gametogenesis

Question 37

Cleavage plane PERPENDICULAR to outer embryo surface

Answer 37

BOTH Daughter cells become Trophoblast cells

Question 38

Trophoblast

Answer 38

- Outer Layer of cells | - Forms EXTRA-embryonic structures (Placenta)

Question 39

Inside-Out Hypothesis

Answer 39

- Fate of Blastomere is determined by its POSITION w/in the Embryo - NOT by Intrinsic properties

Question 40

Two theories of Polarity

Answer 40

1. Inside-Out Hypothesis | 2. Cell Polarity Model

Question 41

Genetics control of cleavage in Invertebrates/Non-mammals Vs. Mammals

Answer 41

Inv: - Controlled through gene products from the MOTHER Mam: - Controlled via the EMBRYONIC genome

Question 42

What happens when an embryo has early cleavage?

Answer 42

- Identical twins | - 2 placentas

Question 43

Purpose of Methylation

Answer 43

When added to specific regions of DNA molecules it Inactivates - Genes - Enhancers - Promoters

Question 44

Angelman Syndrome Characteristics

Answer 44

- Exhibit freq LAUGHTER - Uncontrolled Muscle Movement - Seizures

Question 45

Nanog

Answer 45

- Produces by ICM | - Maintains integrity

Question 46

Cleavage plane PARALLEL to outer embryo surface

Answer 46

- Outer cells -> Troph | - Inner cells -> ICM

Question 47

X-inactivation Characteristics

Answer 47

Once inactivated, remains inactivated - In ALL descendants of the first cell

Question 48

Mutation of Angelman Syndrome is ALWAYS inherited from Whom? How?

Answer 48

From the Mother - Deletion in Long arm of Chrom 15