Specification: Mammals (lec 17)

Question 1

During its migration to the uterus, the ____ ______ prevents the embryo from prematurely adhering to the ______.

Answer 1

Zona pellucida; oviduct

Question 2

(T/F) Cleavage occurs as the embryo travels to the uterus after fertilization.

Answer 2

True!

Question 3

What kind of cleavage do echinoderms and amphibians undergo compared to mammals?

Answer 3

echinoderms and amphibians: radial cleavage

mammals: rotational cleavage

Question 4

What is inner cell mass (ICM)?

Answer 4

the portion of the blastocyst of a mammalian embryo that is destined to become the embryo as it contains embryonic stem cells

Question 5

From morula to blastocyst, the three principal cell types are: _______, _______, and ______ _____.

Answer 5

Trophectoderm; Epiblast; Primitive endoderm (hypoblast)

*epiblast becomes the embryo

Question 6

In a ___________ circuit, the ____/____ dimers activate the Nanog genes.

Nanog proteins then activate _____ ___ as well as genes promoting ________.

Answer 6

Feedforward, Oct4/SOx2

Its own gene; Pluripotency (ICM cell genes)

Question 7

(T/F) Oct4, Sox2, and Nanog are part of an interconnected regulatory circuit in which they activate themselves and each other’s synthesis.

Answer 7

True!

Question 8

Match the EXTRAEMBRYONIC tissues to their definitions:

1) Syncytiotrophoblast
2) Extraembryonic endoderm
3) Amniotic ectoderm
4) Extraembryonic mesoderm

A) Forms the yolk sac needed for nutrition before the placenta forms

B) Lines the chorion, amnion, yolk sac and contributes to blood formation and umbilical cord

C) Will ingress into the uterine tissue to form the CHORION (contributes to the placenta)

D) Encircles the amniotic cavity

Answer 8

Syncytiotrophoblast: Will ingress into the uterine tissue to form the CHORION (contributes to the placenta)

Extraembryonic endoderm: Forms the YOLK SAC needed for nutrition before the placenta forms

Amniotic ectoderm: Encircles the amniotic cavity

Extraembryonic mesoderm: Lines the chorion, amnion, yolk sac and contributes to blood formation and umbilical cord

Question 9

The blastocyst gives rise to:

Answer 9

Trophoblast and Inner cell mass

Question 10

The syncytiotrophoblast rises from:

The extraembryonic endoderm rises from:

The amniotic ectoderm rises from:

The extraembryonic mesoderm rises from:

Answer 10

The syncytiotrophoblast rises from: TROPHOBLAST

The extraembryonic endoderm rises from: Primitive endoderm (hypoblast)

The amniotic ectoderm rises from: Epiblast

The extraembryonic mesoderm rises from: Primitive streak

Question 11

(T/F) Primitive streak gives rise to the embryonic mesoderm, endoderm, and ectoderm.

Answer 11

True!

Question 12

What happens at days 14, 15 and 16 during human gastrulation?

Answer 12

At days 14 and 15, the ingressing epiblast cells are thought to replace the hypoblast cells (which contribute to the yolk sac lining).

At day 16, the ingressing cells fan out to form the MESODERMAL LAYER.

Question 13

Following multiple rounds of whole genome duplication, vertebrates have multiple ____ clusters.

Answer 13

Hox

*there is evolutionary conservation of hox genes from flies to mammals

Question 14

(T/F) Hox genes give identities and are very important for the anterior-posterior regionalization of our spines.

Answer 14

True!

Question 15

The chick has TWICE AS MANY _____ _______ as the mouse.

Answer 15

CERVICAL VERTEBRAE

Question 16

What does

1) complete knockout of Hox 10 paralogues lead to?

2) complete knockout of Hox11 paralogues lead to?

Answer 16

1) complete knockout of Hox 10 paralogues CONVERTS LUMBAR vertebrae (after the 13th thoracic vertebrae) into RIBBED thoracic vertebrae.

2) complete knockout of Hox 11 paralogues TRANSFORMS the SACRAL vertebrae into copies of LUMBAR vertebrae.

Question 17

(T/F) When you knock out hox genes, there is the conversion of the identities of those segments into more posterior-like identities.

Answer 17

False!

When you knock out hox genes, there is the conversion of the identities of those segments into more ANTERIOR-like identities.

Question 18

What happens when

1) splitting occurs before the formation of the trophoblast?

2) splitting occurs after trophoblast formation but before amnion formation?

3) splitting occurs after amnion formation?

Answer 18

1) each twin has its own chorion and amnion

2) twins have individual amniotic sacs but share one chorion

3) twins in one amniotic sac and a single chorion

Question 19

Cleavage differs greatly among the four groups of vertebrates (zebrafish, frog, chicken and mammals).

What kind of cleavage do each undergo?

Answer 19

Zebrafish + Chicken: meroblastic (incomplete) DISCOIDAL cleavage

Frog: holoblastic (complete) unequal (mesolecithal) RADIAL cleavage

Mammals: holoblastic (complete) equal (isolecithal), ROTATIONAL cleavage

Question 20

In the four vertebrates, what has happened by the late GASTRULA stage?

Answer 20

The endoderm is inside the embryo, the ectoderm surrounds the embryo, and the mesoderm is between the endoderm and ectoderm.

The regionalization of the mesoderm has also begun.

*vertebrates are more similar to each other now than at early cleavage.

Question 21

What does SMO stand for? What is it?

Answer 21

Spemann Mangold Organizer

It is a key tissue associated with the region of gastrulation. This tissue helps give signals through morphogens to the various emerging germ layers as they form.

Question 22

1) Which stage follows gastrulation in vertebrates?

2) What characterizes ALL the vertebrates in this stage?

Answer 22

1) The PHARYNGULA STAGE immediately follows gastrulation.

2) The pharyngula stage, with a PHARYNX, a central neural tube and notochord flanked by somites, and a sensory cephalic (head) region characterizes ALL the vertebrates.

*it is after this stage the vertebrate start looking different.

Question 23

Levels of BMP dictate the type of ectoderm formed. What is formed in:

1) Low levels of BMP

2) Moderate levels of BMP

3) High levels of BMP

Answer 23

1) low levels of BMP: neural plate/tube

2) moderate levels of BMP: neural crest

3) high levels of BMP: surface ectoderm (epidermis)

Question 24

What are the four major lineages of mesoderm?

Answer 24

1) Intermediate mesoderm

2) Chorda mesoderm

3) Paraxial mesoderm

4) Lateral plate mesoderm

Question 25

(T/F) The intermediate mesoderm gives rise to the kidney and gonads, the chorda mesoderm gives rise to notochord, the paraxial mesoderm gives rise to head and somite and the lateral plate mesoderm gives rise to the circulatory system, somatic and extra-embryonic.

Answer 25

True!