Devo Bio Chapter 3 : Xenopus Laevis

Front 1

Xenopus laevis: egg
The egg is composed of an animal & a vegetal region, both covered by _________ ________

Back 1

vitelline membrane

Front 2

Meiosis is stopped at ______ ______ with apparent 1 polar body (the 2nd polar body comes after fertilization).
After fertilization, the cortex (the layer below plasma membrane) rotates to determine future dorsal region at a position opposite to the site of ______ ______.

Back 2

1st division; sperm entry

Front 3

Describe the 9 steps associated with Xenopus laevis fertilization and early growth

Back 3

1. one sperm enters animal region
2. completes meiosis
3. egg and sperm nuclei fuse
4. vitelline membrane lifts
5. yolk rotates to down (15 mins)
6. cortical rotation (60 mins). Cortex is layer below plasma membrane
-rotation determine future dorsal region (opposite sperm entry site)
7. 1st cleavage (90 mins) A/V
8. 2nd cleavage (110 mins) A/V 90 degrees to 1st
9. 3rd cleavage (130 mins) equatorial (4 small animal and 4 large vegetal= 8 blastomeres)

Front 4

The blastula (after 12 divisions, thousand's cells) has _______ ______

Back 4

radial symmetry.

Front 5

The______ _______ will become the internalized mesoderm and endoderm.

Back 5

marginal zone

Front 6

Internalization of the mesoderm and endoderm starts at the ________

Back 6

blastopore.

Front 7

Describe the 5 stages involved in gastrulation

Back 7

1) mesoderm and endoderm converge and begin to move inwards at dorsal lip of the blastopore
2) this extends inwards along A/P axis
3) ectoderm spreads to cover embryo= EPIBOLY
4) dorsal endoderm separates mesoderm from the space between the yolk cells = ARCHENTERON (future gut cavity)
5) lateral mesoderm spread ventrally to cover inside of archenteron.

Front 8

During gastrulation, mesoderm and endoderm converge and begin to move inwards at _____ _____ of the blastopore

Back 8

dorsal lip

Front 9

The process by which ectoderm spreads to cover the embryo is called______

Back 9

epiboly

Front 10

dorsal endoderm separates mesoderm from the space between the yolk cells = _________ (future gut cavity)

Back 10

ARCHENTERON

Front 11

Neuralation is the formation of the _____ ______

Back 11

neural tube

Front 12

The neural plate is the _______ located above notochord and somites.

Back 12

ectoderm

Front 13

The edge of the neural plate forms _____ _____ which rise towards midline

Back 13

neural folds

Front 14

The anterior neural tube becomes _____. Mid and posterior neural tube becomes ______ ______.

Back 14

brain; spinal cord

Front 15

Describe in detail the 4 stages of neuralation

Back 15

1) The neural plate is the ectoderm located above notochord and somites.
2) The edge of the neural plate forms neural folds which rise towards midline.
3) The folds fuse to form neural tube.
4) The neural tube sinks below epidermis.
The anterior neural tube becomes brain. Mid and posterior neural tube becomes spinal cord.

Front 16

The dorsal part of ______ become dermatome (future dermis).
The rest of each somite becomes _____ and _____ muscles (and limbs).

Back 16

somites; vertebrae and trunk

Front 17

What are the somites?

Back 17

The somites...
The dorsal part of somites become dermatome (future dermis).
The rest of each somite becomes vertebrae and trunk muscles (and limbs).
Lateral plate mesoderm becomes heart, kidney, gonads and gut muscles.
Ventral mesoderm blood-forming tissues. Also at this stage, the endoderm gives rise to the lining of the gut, liver & lungs.

Front 18

After gastrulation, the early tail bud stage occurs.
In the anterior embryo,
a) the ______ is divided,
b) eyes and ears form,
c) 3 _____ ______ form (anterior arch later becomes the jaw).
In the posterior embryo, the tail formed last from dorsal lip of blastopore by extension of notochord, somites and neural tube.

Back 18

brain; branchial arches

Front 19

Neural crest cells come from the edges of the______ _____ after neural tube fusion.
They detach and migrate as single cells between the mesodermal tissues.
to become these 4 things:

Back 19

neural folds;
1) sensory and autonomic nervous systems
2) skull
3) pigment cells
4) cartilage

Front 20

The vertebrate body plan consists of the________ ______ ______ (segmented vertebral column and skull) and the ______ ______ _____ (including the ventrally located mouth).

Back 20

antero-posterior axis; dorso-ventral axis

Front 21

All vertebrate embryos pass through the _____ ______ when the embryos are all similar in appearance. These embryos share what 3 things in common?

Back 21

phylotypic stage:
These embryos share 1) the head,
2) the neural tube which forms the brain and spinal cord (under which is the notochord, an early mesoderm structure along A/P) and
3) mesodernal somites (blocks of mesoderm flanking the notochord which form the muscles of the trunk & limbs).
The large eggs of fish, frogs and bird have large yolks that provide nutrients to the developing embryo.
Mammalian eggs are small and obtain nutrients from the ovoduct then the placenta.

Front 22

Describe the technique of in situ hybridization

Back 22

Purpose: To determine when and where a particular gene's mRNA is present.
Details: Complementary single-stranded nucleic acid strands (RNA or DNA), commonly known as "probes", will bind tightly (hybridize) to a specific mRNA.
This can be visualized if the probe is labeled (or tagged) with an isotope, a fluorescent dye or an enzyme that produces a coloured substance.
When embryos (or another tissue) are fixed and permeabilized then allowed to undergo such a hybridization reveal the pattern of gene expression.
Whole mount and tissue sections can be visualized.

Front 23

A number of extracellular signals pass from cells of origin to bind the cell-surface of the receiving cells.
These signals include these 9 things

Back 23

FGFs, EGF, TGF-beta, hedgehogs, Wnts, Delta and Serrate (membrane-bound), ephrins (membrane-bound), and retinoice acid

Front 24

What are the 3 main stages of vertebrate development?

Back 24

1) setting up the main body axes (A/P and D/V)
2) specification of three germ layers (endoderm, mesoderm and ectoderm)
3) germ layer patterning (mesoderm and early nervous system)

Front 25

________ ________ provide factors (RNA and proteins) to the egg during oogenesis (including subcellular localization to specific regions.

Back 25

Maternal genes

Front 26

______ ______ are expressed by the embryo's genes.

Back 26

Zygotic genes

Front 27

Xenopus animal/vegetal axis is _______ determined

Back 27

maternally

Front 28

Localized ______ control determination of the animal/vegetal axis in Xenopus. Many are signaling molecules which specify early polarity and induction of the mesoderm.
For example, ______ of the TGF-beta family of growth factors.
_____ is synthesized during early oogenesis and is localized to the ______ _____ of the oocyte.
By early after fertilization, ______ has moved to the vegetal cytoplasm to drive animal/vegetal identity.

Back 28

mRNAs; Vg-1; Vg-1; vegetal cortex ; Vg-1

Front 29

In Xenopus, before fertilization, the egg has a ______ _______.

Back 29

radial symmetry

Front 30

______ ______ sets up the D/V axis with the dorsal side of the embryo situated at a place opposite of the ____ _____ _____

Back 30

Sperm entry; sperm entry point