Mosaic and Regulative Development.

Question 1

Do multicellular organisms use mosaic or regulative development?

Answer 1

They will use both.

They will use them to different degrees.

Question 2

Describe mosaic development?

Answer 2

Mosaic development depends on cytoplasmic determinants.

These are placed in the egg by the mother.

Blastomeres will receive a form of cytoplasmic determinant which will drive gene expression that pushes that cell down a certain pathway.

Question 3

In mosaic development, when does differentiation occur?

Answer 3

Determination occurs during early cleavage.

Question 4

In mosaic development, how does the differentiation of a cell affect the other cells around it?

Answer 4

The differentiation of a cell is independent of other cells.

Question 5

Describe regulative development?

Answer 5

Regulative development relies upon inductive interactions from other cells.

Here the blastomeres are not determined until they receive a signal from another cell.

Cell differentiation is reliant upon other cells and driven by external signals.

Question 6

What kind of cellular signals drives mosaic development?

Answer 6

Internal signals.

Question 7

What kind of determination is regulative development?

Answer 7

Progressive.

Meaning that it occurs over a long period of time.

Question 8

How is cell communication in regulative development often done?

Answer 8

Protein secretion.

Question 9

Protostomes undergo what kind of development?

Answer 9

Mosaic.

Question 10

Deuterostomes undergo what kind of development?

Answer 10

Regulative.

Question 11

Define cytoplasmic determinants?

Answer 11

They are found in the cytoplasm of the egg.

They are differentially segregated amongst blastomeres during cleavage.

They determine the gene expression in the nuclei of daughter cells.

Question 12

Define induction?

Answer 12

Induction is the interactions between cells or tissues that determine the pathway of determination.

Question 13

What is it that determines how the egg develops in mosaic development?

Answer 13

Molecules in the egg.

Question 14

When the fate is sealed by mosaic development, what will the cells look like phenotypically?

Answer 14

The same.

Question 15

Are the cytoplasmic determinants symmetrically laid out through the egg?

Answer 15

No. Symmetrically.

Question 16

What kind of blastomeres make up regulative developers?

Answer 16

Totipotent cells.

Question 17

Asymmetry in regulative developers will influence future development, true or false?

Answer 17

False.

Question 18

Is mosaic development more like epigenesis or preformation?

Answer 18

Preformation.

Question 19

How are PGCs determined in amphibians?

Answer 19

Germ-plasm migrates from the vegetal pole up the cleavage furrow and will enter some of the cells.

These cells are then determined to become PGCs and later gametes.

Question 20

How many cells are in a C.elegans?

Answer 20

959 cells.

Question 21

What do the P.granules in C.elegans contain?

Answer 21

Ribonucleoproteins

Question 22

Describe how the P.granules form PGCs in C.elegans?

Answer 22

After fertilisation, the P granules are uniformly distributed around the zygote.

They will begin to migrate to the right side and the embryo will divide into 2 cells, the AB cell and the P1 cell.

In the P1 cell, the P granules will move to the right side and the P1 cell divides giving a P2 cell.

This process continues until the PGCs are formed.

Question 23

What do the AB cells form in the C.elegans?

Answer 23

The AB cells form muscle and neuron cells.

Question 24

In the developing C.elegans, will SKN-1 be found on the same side as the P granules?

Answer 24

No. Opposite side.

Question 25

What does SKN 1 do?

Answer 25

It determines the muscle cells.

Question 26

What does the yellow crescent in tunicates determine?

Answer 26

Muscle cells.

Question 27

What does the grey crescent in amphibians determine?

Answer 27

Chordamesoderm.

Question 28

In C.elegans, what connects the vulva to the ovary?

Answer 28

The anchor cell.

Question 29

If the anchor cell is destroyed will the vulva develop?

Answer 29

No.

Question 30

If the gonad cell is destroyed, will the vulva develop?

Answer 30

Yes.

Question 31

Is the development of the vulva in C.elegans mosaic or regulative development?

Answer 31

Regulative.

Question 32

What is another name for the C.elegans?

Answer 32

Nematode.

Question 33

What happens to the blastomeres in the nematode that do not get germplasm?

Answer 33

They will undergo chromosome diminution.

Question 34

What is chromosome diminution?

Answer 34

Somatic cells will keep the chromosome fragments with genes relative to that cells particular function.

E.g. A muscle cell will lose all of the non-relevant chromosomes and keep only the DNA relevant to being a muscle cell.

Question 35

What fly does chromosome diminution take place in?

Answer 35

The midge fly.

Question 36

How does chromosome diminution occur in the midge?

Answer 36

One end of the zygote will contain pole plasm and as the cells divide, the cells which get pole plasm will go on to become PGCs and the other cells will form somatic tissues.

Question 37

How are PGCs determined in the midge fly?

Answer 37

One end of the zygote will contain pole plasm and as the cells divide, the cells which get pole plasm will go on to become PGCs and the other cells will form somatic tissues.

Question 38

How have experiments given a sterile midge?

Answer 38

Experiments have tied off the pole plasm end of the zygote.

The cell begins to divide without the pole plasm and this results in a sterile midge.