A technician in Nairobi follows a human cell that has 2n = 46 chromosomes and 2C of DNA in G1 phase…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A technician in Nairobi follows a human cell that has chromosomes and C of DNA in G1 phase. The cell enters mitosis.
- How many chromatids does the cell have in prophase?
- How many kinetochores are joined to spindle fibres at metaphase?
- How many chromosomes does the whole cell have in the middle of anaphase?
- How many chromosomes move to each pole?
Need a reminder? The key ideaShow
Mitosis runs in the order prophase, prometaphase, metaphase, anaphase and telophase. Each chromatid has its own kinetochore. At anaphase the centromeres split, and every chromatid is counted as a chromosome. The whole cell then holds twice the chromosome number of a G1 cell, but the same 4C of DNA.
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. Use the table of the lesson: two chromatids in each chromosome from prophase to metaphase.
Step 1. Prophase. chromatids.
Step 2. Metaphase. Each chromatid has one kinetochore. There are kinetochores.
Step 3. Anaphase. The pairs separate, and the chromatids are now chromosomes. The cell has chromosomes.
Step 4. Each pole. The chromatids go equally to the two poles, .
Answer: ; ; ; .
Check. Each daughter cell will get chromosomes, the same as the parent cell.
Watch out. The chromosomes of anaphase are a short stage. The cell still has only C of DNA.
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