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[HKAL] 請Biology 高手入內解答.
Procedures for amniocentesis:
1. withdrawal of amniotic fluid
culture the foetal cells for 2
3. chromosomal analysis
why is Step 2 necessary?
it to ensure the foetal cells have grown into a suitable development stage for analysis?
- catkan11Lv 71 十年前最愛解答
How many cells do you expect to get from one sample of amniotic fluid? not many, I guess.
When you have many cells, you will have a higher chance to find one dividing. If you look at the pictures from a text book with many cells, most of them the chromosome is invisible.
So your answer is partly right. Bearing in mind that foetal cell division is not synchronized, I would say [the higher cell count] is the main reason for step 2.
2010-04-14 12:07:54 補充：
I think it is not "more time for mitosis".
For the life cycle of a cell, mitosis takes a very brief moment compared with the dormant stages. Given a single cell, it does not need 2 weeks to complete a mitosis process.
2010-04-14 12:12:36 補充：
It is not possible for us to put one cell under observation for a long time to wait for this moment. What we usually do is to scan through all the cells at the same time, and look for one which happens to be under mitosis.
2010-04-14 12:12:59 補充：
You don't really need many cells to confirm chromosomal anormalies. One single cell under the right mitosis stage will do.
The difficulty usually lies in finding "THE" cell with the right timing out of the rest of the cells.
2010-04-14 12:14:34 補充：
By increasing the total number of cells by culturing, you increased the chance of finding one with the right stage. That's it.