Chapter 1

Question 1

Preformation :

Epigenesis :

Answer 1

Preformation : That a person develops from a small person-like thing.
Epigenesis : that a dynamic development occurs from something that is not human shaped

Question 2

Emergent Property :

Answer 2

1: A property which something does not have by itself, but develops when in a complex system.
2: a property of a system which cannot be predicted from its component parts.

Question 3

Mosiac Development vs regulative development

Answer 3

Mosiac Development : Believed there were nuclear determinants, which would get separated into different cells with mitotic divisions. Which Nuclear determinant ended up in a cell would then dictate what it would develop into. If a cell with the nuclear determinant for the arm was killed, then no arm would appear.
Regulative development : That there is a complex regulatory system (which includes but is not limited to cytoplasmic, not nuclear determinants). If a cell was killed the body could adapt to the loss. At least in early stages.

Question 4

What was the reductionist methodology?

Answer 4

The reductionists would look at a single gene and try to figure out its function.

Question 5

What was the problem with the reductionist method of approaching development? What is the solution?

Answer 5

The problem is that genes have emergent properties. In other words genes behave in complex regulatory systems, and you cannot see these complex systems if you are working with a single gene.

Systems biology is the approach of learning whole regulatory systems.

Question 6

Systems biology :

Answer 6

the process of considering multiple genes together in regulatory networks

Question 7

How does cloning show that different cell types run off of similar genetic mechanisms?

Answer 7

You can take a the mitotic spindle from any cell, place it into an unfertilized egg without nuclear material and see successful cloning. This shows that (most) any cell type has the potential to create an organism.

Question 8

Cell differentiation :

Answer 8

Cells reach points where they have committed to a path in development and will not go back. This is when they differentiate.

Question 9

Pattern formation :

Answer 9

Occurs on a higher level then differentation

Question 10

Morphogenesis :

Answer 10

Occurs on a higher level then morphogenesis

Question 11

Arrange in order of complexity :
Growth
Cell Differentiation
Morphogenesis
Pattern Formation

Answer 11

Cell differentiation :
Pattern formation :
Morphogenesis :
Growth :

Question 12

Regulation of growth is still mysterious, why?

Answer 12

Because they do not really know how the body signals to different tissues to grow at different rates.

Question 13

Presumptive thigh tissue is transferred to a wing bud. What happens? What does this indicate?

Answer 13

The presumptive thigh tissue forms a claw at the wings point. Here we see to important things.

1: the tissue turned into claws not a wing, so the tissue has specialized in some way. (epigenetic mechanism, since they have the same code within them)
2: The tissue formed a claw, not a thigh. So we can tell that the signal which indicates distal development is the same in both limb buds, even though they are forming different limbs.

Question 14

Ectoderm:

Answer 14

forms the outer layer of the skin (not all the skin), and the nervous system

Question 15

Mesoderm:

Answer 15

everything which is not a part of the ectoderm or endoderm

Question 16

Endoderm:

Answer 16

forms the lining of the gut (not all the gut)

Question 17

Epithelial to messenchymal

Answer 17

Cells go from a rigid structure connected by adheren junctions, to a mobile form capable of motility and movement. This behavior is also associated with cancer cells if they are going to undergo metastasis.

Question 18

Localized contractions on the outer side of the blastocyte can cause what?

Answer 18

Invagination.

Question 19

Induction in development is

Answer 19

when a cell induces nearby cells to do what it does.

Question 20

Name an example of induction:

Answer 20

Cells where taken from the dorsal lip of a grastula (the region which normally forms the notochord). These cells are stained and translated to a different gastrula. They are placed into a region that would not become the notochord. These cells not only became notochord cells, but also induced the cells nearby them, cells from the host, to become grastula cells as well. Induction.

Question 21

differentiate between permissive and instructive induction.

Answer 21

Permissive induction : This is the cell’s default. It will follow the structure of its nearby neighbors, receiving instruction from the extracellular matrix.

Instructive induction : The cell is given explicit instruction to become something specific. Our example of the notochord was instructive induction, it told its neighbors to become notochord.

Question 22

As cells differentiate and develop specificity, they stop responding to certain signals/morphogens. Name a couple of ways this could happen.

Answer 22

The cell could no longer have the correct surface receptor.

The cell could have the correct surface receptor, but not all of the intermediates in the transduction pathway.

Question 23

Define :

Determination

Answer 23

The point where the cell has decided to become a something specific (epigenetic regulators)

Question 24

Define :

Specification

Answer 24

The fate the cell would acquire if left alone in media, with NO external factors.

Question 25

Define :

Differentiation

Answer 25

The process by which a cell with wide developmental potency becomes a cell with a narrower developmental potency. The normal process by which it gains its properties.

Question 26

Define :

Developmental potency

Answer 26

What the cell could form, totipotent could become anything, pluripotent anything non placental associated, etc.

Question 27

If a determined cell was placed by other cells, what would you expect to find.

Answer 27

You would expect it to still follow the same pathway for differentiation as the cells it came from do.

Question 28

ectopic :

Answer 28

in an abnormal place or position

Question 29

Eye tissue transferred from a gastrula into muscle tissue forms muscle. Eye tissue transferred from neurula (later developmental stage) forms eye tissue in the muscle. What does this say about determination.

Answer 29

This shows that cells become progressively more determined as development continues losing developmental potency.

Question 30

Cell autonomous vs non-cell autonomous. Define a non cell autonomous trait. Say how you could test to see if a trait was cell autonomous.

Answer 30

Cell Autonomous : that the individual cell alone dictates the traits phenotype, without being influenced environment/other cells it is next to.
Ex. A chimera mouse is made from a white furred strain and a brown furred strain, it has a brown and white coat, furthermore it is brown, or white, in the regions which correspond with cells from that coat colors background genetics. Coat color is cell-autonomous.

Question 31

Define asymmetric divisions in development :

Answer 31

It can refer to unequal amounts of cytoplasm going to different cells. But it always refers to unequal amount cytoplasmic determinants ending up daughter cells, one cell having much more than the other.

Question 32

Homologous structures :

Answer 32

Structures which come from the same background. Like the horse leg, which appears different but uses the same bones as my leg or arm. Structures like this can arise through changes in the code which encodes for the developmental pathway, causing a large scale change, with a small mutation in the DNA.