A plant has 18 chromosomes in each cell of its root tip…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A plant has chromosomes in each cell of its root tip.
- How many chromosomes are in a male gamete?
- How many chromosomes are in the zygote?
- How many chromosomes are in the primary endosperm nucleus?
Need a reminder? The key ideaShow
One male gamete fuses with the egg and makes the zygote, . The other fuses with the two polar nuclei and makes the primary endosperm nucleus (PEN), . The two polar nuclei and the egg come from the same megaspore, so they are alike, and the two male gametes are alike. The PEN divides by mitosis, first with free nuclei and later with walls.
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 add the nuclei that fuse.
Step 1. The male gamete. chromosomes.
Step 2. The zygote. A male gamete and an egg fuse: chromosomes.
Step 3. The PEN. A male gamete and two polar nuclei fuse: chromosomes.
Answer: ; ; .
Check. The zygote is , and the PEN is .
Watch out. The PEN is not . It has three sets of chromosomes.
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