In some organisms karyokinesis is not followed by cytokinesis…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
In some organisms karyokinesis is not followed by cytokinesis. Take one such cell with a single nucleus of chromosomes. Its nucleus, and every nucleus formed from it, divides by mitosis times in a row, and no cytokinesis takes place.
- How many nuclei are formed, and in how many cells do they lie?
- How many chromosomes are there in all the nuclei together?
- How many separate nuclear divisions take place in all?
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
(a) Nuclei and cells. Each round doubles the number of nuclei: nuclei. With no cytokinesis the cytoplasm never divides, so all of them lie in multinucleate cell, a syncytium. The liquid endosperm of coconut forms this way.
(b) Chromosomes. Mitosis is an equational division, so every nucleus has chromosomes: chromosomes.
(c) Nuclear divisions. Each division of a nucleus adds one nucleus. Going from to nuclei takes divisions.
Answer: (a) nuclei in cell. (b) chromosomes. (c) nuclear divisions.
Check. Round by round, the divisions are . Their sum is .
Watch out. A syncytium is one cell with many nuclei, not many cells. The number of cells changes only when cytokinesis takes place.
Discussion (0)
Log in to join the discussion.
Loading…