BIOL 303 Study Questions Set 8
1. What are some of the characteristics of C. elegans that make a good model system
for studying developing?
Type one embryogenesis
Immediate activation of zygotic genes
Rapid specification of blastomeres by products of zygotic genes and by maternally
provided transcripts and proteins
Relatively small number of cells at start of gastrulation
2. What type of cleavage is observed in the C. elegans blastula?
Rotational holoblastic (complete)
Cleavage divisions are symmetric
3. What establishes the anterior-posterior axis in the C. elegans egg?
C. elegans are hermaphrodites: having both male and female reproductive parts
Elongated egg shape – defines future anterior-posterior axis > decision for anterior
end relates to position of sperm pronucleus
Sperm centriole initiates cytoplasmic movement that pushes the male pronucleus
to the nearest end – that end will become the posterior pole
4. What is the function of P granules? Is P granule movement dependent of
microtubules or microfilaments? How was this determined?
P-granules: ribonucleoprotein complexes containing translation regulators that
specify the germ cells in C. elegans and are localized by PAR (“partitioning”)
They are initially spread out evenly throughout the cell but after fertilization they
become localized in the posterior.
Inherited by P1 cells after localization. P1 then divides more P granules and they
are inherited by P2 cells. They are then associated with nucleus that then
becomes P3, P4 – forms germ line.
Localization requires microfilaments
Experiment: drug treatment cytochalasin D (disrupts microfilaments) prevents