Biology Forum › Cell Biology › Mitosis
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- November 10, 2006 at 8:53 pm #6273
OoBiologyoOParticipantHi!
Apparently, before counting the # of chromosomes in onion root cells, we can make predictions about the number we are going to find. How is this possible? I am not asking for an answer necessarly, but some pointers would be great!
THANK YOU!
S.
- November 10, 2006 at 10:06 pm #58811druidParticipant
Possibly you can predict the number of chromozomes you’ll see by searching the web for "Allium cepa chromosome number".
It’s almost surely you’ll find in 2 seconds that 2*n = 16🙂
- November 10, 2006 at 10:10 pm #58813OoBiologyoOParticipant
Well, the problem is that we are supposed to predict the number of chromosomes by ourselves, meaning without using existing data…
Apparently, something about onion root cells should lead us to a number close to 18… - November 10, 2006 at 10:16 pm #58815druidParticipantquote OoBiologyoO:Apparently, something about onion root cells should lead us to a number close to 18…
No.
Apparently due to actively dividing cells at root tips, you’ll catch cells at mitosis with 4*n number of chromosomes ( at metaphase for example ). - November 10, 2006 at 10:25 pm #58816OoBiologyoOParticipant
Ok, so this would be one way of predicting. We can look at cells in mitosis, and count the chromosomes, and then divide…
Would there be any other way? - November 10, 2006 at 10:40 pm #58818druidParticipantquote OoBiologyoO:Ok, so this would be one way of predicting. We can look at cells in mitosis, and count the chromosomes, and then divide…
Would there be any other way?It seems i don’t really understand your question.
Do you mean the following task: "Given name of a species, predict number of chromosomes it has." ? - November 10, 2006 at 10:47 pm #58820OoBiologyoOParticipant
No, basically in class we looked at cells in mitosis from an onion root.
We found that, on average, there were 18 chromosomes per cell in anaphase.
But they ask us, if we didn’t have a microscope, how we could predict the number of chromosomes we were going to find… - November 10, 2006 at 11:19 pm #58821druidParticipant
Well, that you’ve got 18 on avarage is due to blurred vision ;).
Number of chromosome in species is constant ( Usually incorrect number of chromosomes leads to death of the cell ).Onion’s haploid set is 8 chromosomes, diploid set is 8*2=16 chromosomes.
At anaphase you cannot distinguish between sister chromatids thus the apparent number of chromosomes is not changed, that is it remains 16.Without microscope you can predict the number of chromosomes at any stage of cell cycle by the following rule ( for diploid organism ):
[interphase]–> 2N –[synthesis]–> 4N —[mitosis]–> 2N —> [interphase]
where N is haploid number of chromosomes.
Anyway you have to know N from observation or database. - November 11, 2006 at 5:27 pm #58865OoBiologyoOParticipant
Actually, I may have mixed up 16 and 18, so yes you might be right there!
So, there is no way of knowing how many chromosomes an onion cell has, unless we look with a microscope or search for existing data?
- November 11, 2006 at 6:13 pm #58871druidParticipantquote OoBiologyoO:So, there is no way of knowing how many chromosomes an onion cell has, unless we look with a microscope or search for existing data?
If you discover something else, please post it here.
- November 11, 2006 at 7:17 pm #58875MrMisteryParticipant
there is a way of aproximating the degree of poliploidy in higher plants, maybe your teacher expects of answer of this type. though i have never heard of poliploid onion..
- November 12, 2006 at 12:15 am #58882druidParticipant
I would answer so:
1. If the cell observed is in
phase=[interphase..gap1] it has 2*8=16 chromosomes.2. If the cell observed is in
phase=(synthesis..metaphase) it has 2*8*2=32 chromosomes which appear to be 16 chromosomes.3. If the cell observed is in
phase=[anaphase..cytokinesis] it has 16+16=32 chromosomes which will be observable because they have been separated by the spindle and moving to opposite directions.Reminder:
[, ] including ends
(, ) excluding endsIf something’s gone wrong with cell devision another numbers can appear, so the above statements are only hypoteses.
- November 12, 2006 at 12:53 am #58886MethalParticipantquote OoBiologyoO:No, basically in class we looked at cells in mitosis from an onion root.
We found that, on average, there were 18 chromosomes per cell in anaphase.
But they ask us, if we didn’t have a microscope, how we could predict the number of chromosomes we were going to find…Personally that sounds like a really stupid question. We DO have microscopes, no reason not to use them. without them we wouldnt even know what a chromasome was…
- November 12, 2006 at 3:07 pm #59296OoBiologyoOParticipant
I know, lots of things are wrong with this class. But I complained enough (politely), and I don’t want them to hate me 😕
I’m a good student, and it’s not my habit to go on discussion boards to get answers to my homework, but here, without any lecture or pointers or helpful lab notebook, I have no choice really…Thank you so much for your help, all of you! Druid, I will try your answer! I will be sure to come back and tell you what the expected answer is.
Thanks!
- December 12, 2006 at 5:04 pm #62550OoBiologyoOParticipant
I guess this was the correct answer, since I got an A =)
THANK YOU!
- December 23, 2006 at 8:53 am #63726Frank MensahParticipant
I discovered that, for a zygote to be formed, a haploid number of chromosomes should come from each parent for the diploid number to be restored in the zygote.Also, mitosis undergoes four main stages; pro phase, meta phase, ana phase and telophase
- December 23, 2006 at 9:03 am #63727Frank MensahParticipant
the number of chromosomes in a human is 46. hence, 2n=46 where n is haploid number.
- December 23, 2006 at 9:08 am #63728Frank MensahParticipantquote Frank Mensah:I discovered that, for a zygote to be formed, a haploid number of chromosomes should come from each parent for the diploid number to be restored in the zygote.Also, mitosis undergoes four main stages; pro phase, meta phase,anaphase and telophase
😛
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