The root-tip cells of a plant have 16 chromosomes each…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
The root-tip cells of a plant have chromosomes each.
- How many chromosomes are in the egg cell?
- How many chromosomes are in the central cell, taking both polar nuclei together?
- How many chromosomes are in all eight nuclei of the embryo sac together?
Need a reminder? The key ideaShow
An ovule has one megaspore mother cell (MMC), which is diploid. The MMC divides by meiosis into four haploid megaspores. In most plants, one is functional and three degenerate. The functional megaspore divides by mitosis three times, with no walls, to make 8 nuclei. The mature embryo sac has 7 cells: the egg, 2 synergids, 3 antipodals and the central cell with 2 polar nuclei.
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.
Given. .
Plan. Find , then count the nuclei in each part.
Step 1. The egg cell. chromosomes.
Step 2. The central cell. It has two polar nuclei of each, so chromosomes.
Step 3. All the nuclei. Eight nuclei of each give chromosomes.
Answer: ; ; .
Check. The central cell holds , the same as a diploid cell, although its nuclei are haploid.
Watch out. Do not treat the polar nuclei as one diploid nucleus.
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