#Question id: 5674
#Unit 5. Developmental Biology
Following statements are regarding to the mechanism of migration of pollen tube.
A. The embryo sac is the product of three mitotic divisions of the diploid megaspore; it comprises seven cells and eight haploid nuclei.
B. The two polar nuclei in the central cell will fuse with the second sperm nucleus and produce the endosperm that will nourish the egg. The other six cells, including the egg, contain one haploid nucleus each.
C. After compatible pollen germinates, the pollen tube grows toward the micropyle.
D. The three cells from the pollen are connected to one another at the tip of the tube, and waves of sodium ions play a key role in the growth of the tube.
Which of the following combinations are correct?
#Question id: 5546
#Unit 5. Developmental Biology
By the end of _______________ , distribution of cells into the three primary tissue types has been completed
#Question id: 1562
#Unit 4. Cell Communication and Cell Signaling
________ are cells of the mammalian innate immune response that help destroy tumors.
#Question id: 4690
#Unit 3. Fundamental Processes
Which of the following of the cleavage enzymes of rRNAs and tRNA is a ribozyme?
#Question id: 2655
#Unit 2. Cellular Organization
Lac Operon will be turned on when