Onion root-tips bathed in suspected water for 48 hours, what was observed appeared to be dense abnormal prophase (B) as well as dense metaphase (A), also abnormal.
A is possibly sticky chromosmes at Anaphase and not metaphase as the chromatids are already migrating to opposite poles. B. is an abnormal stage in prophase. For clearity and easy identification of the abnormal chromosomes i suggest that the magnification be increased. Thank you
Cyto- and genotoxic tests on onion root-tips are usually based on tracking abnormal anaphases and telophases. One should be very careful about discussing abnormal prophases and metaphases in light of onion genotoxicity test.
I see no clear anomaly. Do you suspect chromosome hypercondensation in metaphase? You should check controls carefully.
A is possibly sticky chromosmes at Anaphase and not metaphase as the chromatids are already migrating to opposite poles. B. is an abnormal stage in prophase. For clearity and easy identification of the abnormal chromosomes i suggest that the magnification be increased. Thank you
Yes, should be very careful with prophases and metaphases in onion tests
What about the frequency of such abnormalities, comparing with controls? What about the source of your onions, from the market? You should use organic onions.
A looks more like an abmnnormal anaphase and B like slightly abnormal prophase or beginning early metaphase, but its hard to tell in this low resolution picture. Whether this resembles genotoxicity is also hard to tell. First questions to be answered should be: Are this figures sighificantly increased repeatedly in your samples? Does it affect viability of the cells? Is there an increase in micronuclei or is only mitosis affected?
It is impossible to say anything by getting stuck on two abnormal pictures! It is necessary to have a look at the whole picture. The rate of each abnormalities in every mitotic phases are of importance.
I do not have experience with onion roots. If you want to confirm the damage I would suggest to use the suspect water on a different type of cell and analyze classical cytogenetic endpoints.
You should carefully evaluate all of your findings in comparison to the controls.
First i have to suggest you to increase magnification and observe the preparation, if you find the same this may be due to the presence of sticky chromosomes.
Observation of metaphase-anaphase (lagging piece of chromosomes), telophase (chromosome bridges), and most importantly presence of micro nuclei will tell if DNA damage (double strand breaks) are around. Don't forget that in normal condition cells do not enter mitosis with unrepared DNA damage due to Checkpoints.
The magnification should be increased for a clear view. B not any type of aberration and it is a prophase stage. And for A, simply the cells are elongated bcoz of pressurised tapping or may be due to stickiness.
As others have already remarked, one image is not enough evidence - does this happen in many preps or just this one? All the other cells in this view look OK, so I think it's mechanical damage from tapping or pressing. 'A' looks like an anaphase as others have commented. 'B' looks like a prophase, possibly with several nucleoli visible, but all rolled up into a sausage-like structure. Hope this helps!
To confirm this i suggest u to run alkaline comet assay for the root tips. light microscopy only provide morphological information compared to other techniques of microscopy such as fluoresence (DAPI) that can differentiate normal and ruptured DNA.
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