Pattern formation and cell death

Question 1

o Fate mapping also revealed that ___ cells die during the development of C. elegans.
oThis programmed cell death is called _____.

Answer 1

131

Apoptosis

Question 2

How is apoptosis regulated? (3)

Answer 2

o Apoptosis is regulated by a single gene that is similar between organisms.
o Structures that no longer offer an advantage are targeted for cell death.
o The webbing between fingers of most mammals is eliminated via apoptosis.

Question 3

o In some cases a structure functions in early stages and is _____ during later development.
o The tail of a tadpole undergoes apoptosis during ______.
o Extra ____ are eliminated by apoptosis in humans as the embryo ages.

Answer 3

Eliminated
Metamorphosis.
Neurons

Question 4

What did work by Hans Spemann show?

Answer 4

Work by Hans Spemann showed that the first two cells of a frog embryo are totipotent.

Question 5

Define totipotent.

Answer 5

Totipotent- can develop into all the different types of cells for that species.

Question 6

o In mammals the first ___ cells are totipotent.

Answer 6

eight

Question 7

How do identical twins form?

Answer 7

o Identical twins result from totipotent cells if they separate before the trophoblast and inner cell mess is differentiated.

Question 8

How is cell fate fixed?

Answer 8

Cell fate is generally fixed by late gastrulation.

Question 9

Why are cytoplasmic determinants important?

Answer 9

o Cytoplasmic determinants found in the grey crescent are important for totipotency of the first two cells

Question 10

What did Spemann discover about the cells of the gastrula?

Answer 10

Spemann also discovered that cells of the gastrula can induce pattern formation - arrangement of
tissues and organs in the three-dimensional space.

Question 11

What are organisers?

Answer 11

Cells that can induce pattern formation are called organizers.

Question 12

Biologists later discovered that Spermann’s organizers contained a protein called………..

Answer 12

Bone Morphogenic Protein 4.

Question 13

What is Bone Morphogenic Protein 4 (BMP-4) ?

Answer 13

Bone Morphogenic Protein 4 (BMP-4) is a growth factor hormone that get inactivated in the dorsal side.

Question 14

What does inactivation of Bone Morphogenic Protein 4 (BMP-4) lead to?

Answer 14

Inactivation of BMP-4 allows these cells to form dorsal structures such as notochord and neural tube.

Question 15

Spemann discovered that cells of the ____ __ triggered gastrulation of the surrounding tissue.

Answer 15

dorsal lip

Question 16

What is the role of inductive signals in pattern formation?

Answer 16

Inductive signals play a major role in pattern formation, a crucial step in Morphogenesis.

Question 17

What is positional information?

Answer 17

o The molecular cues (morphogens) that control pattern formation are called positional information.
> This information tells a cell where it is with respect to the body axes.
> It determines how the cell and its descendants respond to future molecular signals.

Question 18

To understand positional information, we will consider the development of a chick limb. How do we the wings and legs of chicks develop?

Answer 18

o The wings and legs of chicks, like all vertebrate limbs, begin as bumps of tissue called limb buds.

Question 19

Which two regions have profound effects on the pattern formation of chick limbs?

Answer 19

Two regions have profound effects on the pattern formation of chick limbs and are the Apical ectodermal ridge (AER) and the Zone of polarizing activity (ZPA)

Question 20

What is the Apical ectodermal ridge (AER)?

Answer 20

Apical ectodermal ridge (AER) is the thickened ectoderm at the bud’s tip.

Question 21

What is the Zone of polarizing activity (ZPA) ?

Answer 21

Zone of polarizing activity (ZPA) is the mesodermal tissue under the ectoderm where the posterior side of the bud is attached to the body.

Question 22

What does the information in the AER region and ZPA region indicate?

Answer 22

The positional information in both regions indicates the precise location of all components of the limb along three axes

Question 23

What signal protein does AER secrete? (2)

Answer 23

o AER secretes a signal protein called Fibroblast growth factor (FGF).
o Removing AER blocks limb outgrowth.

Question 24

What signal protein does ZPA secrete? (2)

Answer 24

o ZPA secretes a signal protein called Sonic hedgehog.
o Tissue transplantation experiments support the hypothesis that the ZPA produces an inductive signal that conveys positional information indicating “posterior” structures.