W5

Question 1

Mechanisms of cell-cell communicaiton.

Answer 1

1. diffusion
2. direct contact (animals only)
3. Gap junction (animals only)
   4 Plasmodesmata (plants)

Question 2

In Drosophila, the first nucleus divisions happen within one cell. What is it called?

Answer 2

cyncytiales Blastoderm.

Question 3

What happens to the Drosophila germcells?

Answer 3

By the time there are about 10 cell nuclei, Pole cells become separated and divide independently.

Question 4

What factor is responsible for the differentiation of germ cells and soma cells.

Answer 4

Because of asymmetrical cleavage with P-Granula going to only one daughter cell: the germ cell.

Question 5

Which mRNAs are responsible for the poles of the Drosophila Cyncyte?

Answer 5

Oscar(posterior) and Bicoid (anterior)

Question 6

What role does Oskar play in the Drosophila Cyncyte?

Answer 6

It determines the posterior end and is essential to the development of the germ cells.

Question 7

Migration of Primordial Germ Cells (PGC) in Drosophila

Answer 7

Are segregated very early. Go on a complex journey, through “Hinterdarm, mesoderm” etc. If they are faulty, they don’t make the migration.

Question 8

Oogenesis in mammals.

Answer 8

PGCs also migrate and end in the Ovare, where they proliferate.
Primary oocytes are frozen at eh Meiose I, only continue to Miose II at puberty.

Question 9

Spermatogenesis in mammals

Answer 9

PGC land in testis, development stopped.
After birth increase in testis through Mitose - build stem cells- build spermatocytes - through Meiose I and II - Spermatiden - sperm

Question 10

Why are spermatids joined?

Answer 10

Because they are haploid, some lack the X chromosome. they need to be joined so that they all get X information.

Question 11

What is “generationswechsel”

Answer 11

The occurrence in the diploid sporophyte folowed and haploid gametophyt.

Question 12

In angiosperms, how is pollen made?

Answer 12

1. Stamen produces Mirosporangium.
2. in microsporangium, mirospores.
3. microspores released - pollen.

Question 13

What are the niche cells in the anther (top of stamen which produces pollen)?

Answer 13

Tapetum

Question 14

Why are tapetum cells important?

Answer 14

Adding Barnase promoter destroys tapetum makes sterile male plants. Adding barnstar to the mutant makes it fertile again.

Question 15

Why is hybridisation desirable.

Answer 15

Hybrids are stronger and

Question 16

What is a spore?

Answer 16

A spore is a multi-celled haploid organism which produces gametes.
Microspore (male) produces microgamete (sperm)
Megaspore (female) produces egg.

Question 17

Sporophyte: Sporogenese

Answer 17

2n - meiose - 1n

Question 18

Gametophyt: Gametogenese

Answer 18

1n - Mitose - 1n

Question 19

Only one cell in the embryo sack becomes functional megaspore. What are the important factors?

Answer 19

Positional information. MAC1 in mase important for lateral inhibition.

Question 20

In Archesporendifferenzierung, what are the mutants?

Answer 20

ems1, tpd1. lead to lack of Tapetum.

Question 21

Why are gametophyte genes hard to identify?

How is this solved?

Answer 21

The don’t behave in a mendellian way.

This is now being solved by the insertion of a mutation system like T-DNA and transposons.