W5 Flashcards
(21 cards)
Mechanisms of cell-cell communicaiton.
- diffusion
- direct contact (animals only)
- Gap junction (animals only)
4 Plasmodesmata (plants)
In Drosophila, the first nucleus divisions happen within one cell. What is it called?
cyncytiales Blastoderm.
What happens to the Drosophila germcells?
By the time there are about 10 cell nuclei, Pole cells become separated and divide independently.
What factor is responsible for the differentiation of germ cells and soma cells.
Because of asymmetrical cleavage with P-Granula going to only one daughter cell: the germ cell.
Which mRNAs are responsible for the poles of the Drosophila Cyncyte?
Oscar(posterior) and Bicoid (anterior)
What role does Oskar play in the Drosophila Cyncyte?
It determines the posterior end and is essential to the development of the germ cells.
Migration of Primordial Germ Cells (PGC) in Drosophila
Are segregated very early. Go on a complex journey, through “Hinterdarm, mesoderm” etc. If they are faulty, they don’t make the migration.
Oogenesis in mammals.
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.
Spermatogenesis in mammals
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
Why are spermatids joined?
Because they are haploid, some lack the X chromosome. they need to be joined so that they all get X information.
What is “generationswechsel”
The occurrence in the diploid sporophyte folowed and haploid gametophyt.
In angiosperms, how is pollen made?
- Stamen produces Mirosporangium.
- in microsporangium, mirospores.
- microspores released - pollen.
What are the niche cells in the anther (top of stamen which produces pollen)?
Tapetum
Why are tapetum cells important?
Adding Barnase promoter destroys tapetum makes sterile male plants. Adding barnstar to the mutant makes it fertile again.
Why is hybridisation desirable.
Hybrids are stronger and
What is a spore?
A spore is a multi-celled haploid organism which produces gametes.
Microspore (male) produces microgamete (sperm)
Megaspore (female) produces egg.
Sporophyte: Sporogenese
2n - meiose - 1n
Gametophyt: Gametogenese
1n - Mitose - 1n
Only one cell in the embryo sack becomes functional megaspore. What are the important factors?
Positional information. MAC1 in mase important for lateral inhibition.
In Archesporendifferenzierung, what are the mutants?
ems1, tpd1. lead to lack of Tapetum.
Why are gametophyte genes hard to identify?
How is this solved?
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.
