47.1 Cleavage

Question 1

cleavage

Answer 1

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)

Question 2

blastomeres

Answer 2

smaller cells from cleavage of zygote

Question 3

first 5-7 divisions=

Answer 3

makes a cluster of cells with blastocoel forming

Question 4

blastocoel

Answer 4

fluid filled cavity within the blastula

Question 5

blastula

Answer 5

hollow ball of cells

Question 6

what causes early cell differentiation

Answer 6

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

Question 7

yolk

Answer 7

stored nutrients

• has polarity (uneven distribution)
• its uneven distribution creates different plans of division of zygote

Question 8

yolk is often concentration in the

Answer 8

vegetal pole

Question 9

yolk concentration decreases at

Answer 9

animal pole

Question 10

animal vegetal axis=

Answer 10

anterior posterior axis

Question 11

lighter cytoplasm (gray crescent )
-formed by cortical rotation

Answer 11

future dorsal side

Question 12

cortical rotation

Answer 12

plasma membrane and associated cortex rotate with respect to inner cytoplasm