47.1 Cleavage Flashcards
1
Q
cleavage
A
period after fertilization of rapid cell division
that divides the zygote (1 large cell) into blastomeres (smaller cells)
-cells carry out S and M phase but skip G1/G2 (so embryo doesn’t really get bigger)
2
Q
blastomeres
A
smaller cells from cleavage of zygote
3
Q
first 5-7 divisions=
A
makes a cluster of cells with blastocoel forming
4
Q
blastocoel
A
fluid filled cavity within the blastula
5
Q
blastula
A
hollow ball of cells
6
Q
what causes early cell differentiation
A
during cleavage (dividing cells)
- different regions of cytoplasm end up in different blastomeres
- so different concentrations of cytoplasmic determinants (mRNA or proteins…) make different developmental events later
7
Q
yolk
A
stored nutrients
- has polarity (uneven distribution)
- its uneven distribution creates different plans of division of zygote
8
Q
yolk is often concentration in the
A
vegetal pole
9
Q
yolk concentration decreases at
A
animal pole
10
Q
animal vegetal axis=
A
anterior posterior axis
11
Q
lighter cytoplasm (gray crescent ) -formed by cortical rotation
A
future dorsal side
12
Q
cortical rotation
A
plasma membrane and associated cortex rotate with respect to inner cytoplasm
