Observing Mitosis in Onion Root Tips Purpose: To observe the stages of mitosis in the cells of actively growing onion root tips. Materials needed for each group: - Onion root tips microscope - toluidine blue stain
- safety goggles - probe
- metric ruler - paper towels
- forceps - apron
-
- scalpel
- 2 glass slides with plastic coverslips
- stopwatch or clock with a second hand
- 3 small beakers (50 or 100 ml) 25ml ratio)
- ethanol/acetic acid fixative (75ml /
- 5M Hydrochloric acid (30 ml H 2O / 20 20 ml ml conc concen entr trat ated ed HCl HCl))
- shar sharp p mind minds s and and a foc focus used ed dem demea eano norr
Procedure: 1.)
Carel Careless essnes ness, s, rowd rowdy y behav behavior ior,, or being being unab unable le to pay pay attent attention ion to wha what’s t’s goin going g on around around you you can can get someone hurt in this lab. Any of these behaviors are unacceptable, unacceptable, and will result in immediate removal from the lab area. Please get yourself in the correct frame of mind now!
2.)
Put on your safety goggles and lab apron. The fixative solution and hydrochloric acid we will be using during this lab are very corrosive, which means that goggles are required at all times. If you spill any material, please let me know immediately. You are required to wash your hands when finishing the experiment.
3.) 3.)
Make Make sur sure e that that you you hav have e 3 bea beake kers rs,, and and tha thatt they they are are labe labele led d fixative, hydrochloric acid, and water.
4.)
Bring Bring the the beaker beakers s up front front and and obtai obtain n 10 ml of of each each substa substance nce.. Your Your teache teacherr will will pour pour these these mater materia ials ls for you.
5.)
Using Using the the forcep forceps, s, place place 2 onio onion n root root tips tips into into your your hydroc hydrochlo hloric ric acid acid bea beaker ker,, and let let them them sit sit for 4 minutes.
6.)
After After 4 minutes, minutes, remove remove the the tips tips from the HCl with the forceps forceps and place place them them in in the the fixat fixative ive solution solution for 4 minutes.
7.)
After After 4 minut minutes, es, remov remove e the tips from the fixative fixative and place place each each one one on a clean clean glass glass slide. slide. Holding Holding the root tip with the forceps, use the scalpel to cut off about 1mm from each root tip. Use the ruler to measure this length. CAUTION: the scalpel is extremely sharp, so make sure your finger is clear when you make the cut. Discard the rest of the root tip, leaving the 1mm piece on your slide.
8.)
Place Place the the glass glass slid slide e on a paper paper towe towel, l, and and add add 2 drops drops of toluid toluidine ine blue blue stai stain n to the the root root tip. tip. Allow Allow the the stain to sit for 2 minutes, and then gently use a paper towel to soak up the excess stain surrounding the root tip. CAUTION: toluidine blue is a stain and will not come out of your clothes – be careful!
9.)
Place Place 2 drops drops of wat water er on on the the root root tip tip and and gent gently ly cove coverr with with a cove coverr slip slip..
10.)
Place Place a paper paper towel towel over over the slide, slide, and and use the the eraser eraser end end of your your pencil pencil to to gently gently press press down down on the the cover slip. This will squash the root tip, making the cells more easily viewable. viewable. CAUTION: DO NOT push so hard as to break the cover slip or slide!
11.)
Using Using a microsc microscope, ope, obser observe ve the onion root tip tip cells cells (remember (remember your micros microscope cope skill skills s from 1 st semester!). Look for cells undergoing the different stages of mitosis under med or high power. Draw
labeled diagrams of these cells on the back of this paper, and call your teacher over to observe these cells, and to sign your paper. 12.)
Clean and dry your microscope slides, cover your microscope and put it away in the cabinet, organize your lab materials, and wipe down your lab station with a paper towel. Wash your hands using soap and water for a minimum of 30 seconds!
