why we should preserve the onion root tips in 70precent alcohol
Answers
Answer:
Keep the root tips in the fixative for 24 hours and then transfer them to 70% ethanol (for preservation and use in future). Onion root-tip cells have a cell cycle of approximately 24-hour duration, i.e., they divide once in 24 hours, and this division usually takes place about two hours after sunrise.
Explanation:
Ethanol (96-100%) is an excellent killing agent and preservative, and is ideally combined with cold for optimum preserving conditions for keeping DNA preserved for over a hundred years. But, the percentage (concentration) of the ethanol is critical. Ethanol drives out water from the tissue and cells, thus dehydrates the tissue and so preserves DNA. 70% ethanol is often used instead of 96-100% because it is cheaper and keeps specimens somewhat flexible, allowing for later morphological study. 70% ethanol however also means that there is 30% of unsolicited things in
the liquid (mostly water), and this may cause degradation of DNA. DNA is actually better preserved with dry specimens, than with material stored at 70% ethanol. In general tissue will remain OK for DNA based work with 1-2 years stored sample in 70% ethanol, whereas dry specimen can be used up to 10 years old with
a similar success rate.