Biol 303- Mod 6 Flashcards
C. elegans
Size:
Culture:
Size: just over 1mm
Culture: agar plates covered with E. coli (bacterial plates) - can also be grown in liquid broth with E. coli
The C. elegans adult is ?that all cells are visible by light (phase contrast or DIC) microscopy.
The C. elegans adult is small enough and thin enough that all cells are visible by light (phase contrast or DIC) microscopy.
Culture: ?
Size:?
Crosses: ?
Generation time: ?
Lifespan: ?
No. progeny: ?
Markers: ?
Culture: agar plates covered with E. coli (bacterial plates) - can also be grown in liquid broth with E. coli
**Size: just over 1mm
Storage of strains: can be frozen
**Crosses: population is 99% “selfing” hermaphrodites
Generation time: 3 days (20C) kept between 16&25C
**Lifespan: reproduce for 3-4 days but live two more weeks
***No. progeny: 250-1000 per hermaphrodite (lower if herm selfed, higher with cross to males, limited by the production of sperm in the herm.)
**Markers: ample visible markers (usually things like body shape, movement)
C. elegans
males are present at ~ ?of the population and result from ?
(hermaphroditic females = XX / males = XO)
males are present at ~ 1% of the population and result from X chromosome non-disjunction (hermaphroditic females = XX / males = XO)
C. elegans is a hermaphrodite
during earlier stage of development ?
– the sperm are ?
later in development the hermaphrodite ?
the distal tip of the ovary is a ?
during earlier stage of development the hermaphrodite produces sperm and these are stored in the spermatheca – the sperm are non-flagellate crawling amoeboid-like cells
later in development the hermaphrodite switches to egg production (oogenesis)
the distal tip of the ovary is a syncytium, oocyte nuclei are bound by plasma membrane and bud off from the syncytium
Diakinesis ?
C. elegans oocytes develop within a synctium and ?
Diakinesis = late prophase C. elegans oocytes develop within a synctium and undergo cellularization as they move down the ovary.
C. elegans is a hermaphrodite
the oocytes (arrested in ?) are moved down the ?
Fertilization triggers the ?
polyspermy is thought to be blocked by ?
the oocytes (arrested in prophase of 1st meiotic division ) are moved down the ovary and are fertilized as they are pushed through the spermatheca. Fertilization triggers the completion of meiosis.
polyspermy is thought to be blocked by rapid deposition of chitin over the egg
Generation time: ?
Lifespan: ?
No. progeny: ?per hermaphrodite (lower if ?, higher with c?, limited by the ?)
Generation time: 3 days (20°C)
Lifespan: reproduce for 3-4 days but live two more weeks
No. progeny: 250-1000 per hermaphrodite (lower if selfed, higher with cross to males, limited by the production of sperm in the hermaphrodite)
Genome size ?
Total number of genes ~ ?
Number of genes required for development ~ ?
C. elegans has Hox genes, ?
Nervous system: has a simple nervous system (? neurons)- exhibits ?
Genome size 97 Mb
Total number of genes ~ 19,000
Number of genes required for development ~ 1700
C. elegans has Hox genes, TGF-b, Wnt, and Notch signalling pathways (found by exhaustive RNAi feeding screens)
Nervous system: has a simple nervous system (302 neurons)- exhibits simple behaviour (limited) and rudimentary learning
Markers: ?
Markers: ample visible markers (usually things like body shape, movement)
egg is only ? long (10X smaller than the ?)
egg is only 50 microns long (10X smaller than the Drosophila egg)
Invariant embryonic development: C. elegans adult male or hermaphrodite displays ? that arise through ?. Thus, the lineage of any cell in the adult is known and can be ?.
Invariant embryonic development: C. elegans adult male or hermaphrodite displays an exact number of cells (959 for the herm, 1031 for the male) that arise through reproducible patterns of cell division. Thus, the lineage of any cell in the adult is known and can be traced back to the first division.
Cell ablation studies possible: ?
RNAi: works extremely well - even using E.coli expressing dsRNA as food source - ?
Cell ablation studies possible: based on the known and invariant lineage pattern of development, and because all cells are visible, laser ablation of specific cells has been a powerful tool
RNAi: works extremely well - even using E.coli expressing dsRNA as food source - some spreading and perdurance of the RNAi effect into next generation (RNAi is not mutagenic - RNAi may also not be specific to just one gene)
“type one” embryogenesis
sea urchins (?), snails (?), ascidians (?), and C. elegans (?)
immediate activation of ?
small number of cells at ?
what? occurs in situ, by both ? and ? mechanism
lineage plays an important role in ?
sea urchins (echinoderms), snails (gastropods molluscs), ascidians (tunicates, sea squirts), and C. elegans (nematode)
immediate activation of zygotic genes
small number of cells at start of gastrulation (C.elegans = 26-28)
rapid blastomere specification occurs in situ, by both autonomous and conditional mechanism
lineage plays an important role in the spatial organization of the early embryo
Invariant embryonic development: ?
(very unlike Drosophila where ?)
autonomous specification ?
conditional specification ?
Invariant embryonic development: frequently mosaic-like and cell fate is specified on a cell-by-cell basis (very unlike Drosophila where gradients of morphogens are used to create positional information over fields of cells)
autonomous specification directly tied to asymmetric divisions (unequal distribution of cytoplasmic determinants)
conditional specification via cell-cell interactions (regulative development) is also used
