1997 WWLPT Biology Institute: Life Cycles:
Reproduction & Embryological Development
Target Age or Ability Group Audience
Teacher Instructions/Special Precautions
Materials & Equipment Needs
Background [Prior Knowledge
or vocabulary necessary to complete activity]
The Student Lab
Method of Evaluation/Assessment
Meiosis (Microsporogenesis) in
Common Plants and Animals.
Mitosis (normal cell division)
is an important process in biology because of its roles in asexual reproduction,
growth, and development. As a result, many biology students observe
cells in the different stages of mitosis by preparing onion root tip slides.
Students usually enjoy these labs because they get to prepare the slides
themselves. They can see and touch the materials that they are using
and go through the process of preparing the slides.
The process of meiosis is an essential
part of sexual reproduction in higher plants and animals. Unfortunately,
hands-on meiosis labs are not common. Activities involving drawings,
paper cut-outs or plastic "chromosomes" are used in place of a true hands-on
lab involving real plants and animals. If you have a student or group
of students that wish to work beyond the typical dry meiosis labs and try
a wet meiosis lab where they make their own slides and look for meiotic
divisions, the following lab activities may be useful.
lab activities were designed to:
1. encourage biology teachers to do hands-on biology labs,
2. allow students to identify and collect readily available sources
of plant and animal materials,
3. provide an inquiry based lab procedure that advanced biology students
can use with practice and patience.
Target Audience or Age Group
Grade Level: For High School Students taking an Advanced Biology or Genetics
course . This investigation activity could also be used for an independent
Notes to the Teacher:
Requires patient students that have used compound microscopes before.
Preparation time needed - The plant buds and animal testes need to be collected
in the late spring and early summer, when meiosis is most to be occurring.
The buds and testes can be stored in fixative for at least a year.
All the material from the plants and animals needs to put in fixative (3:1
fixative consisting of 3 parts 100% ethanol and 1 part glacial acetic acid)
for several days to bleach out any pigment present.
Class time needed - In a 45 - 60 minute period, 7 - 10 slides can
be made. The observation time needed to check the slides for meiosis
can take another 30 -60 min.
If petroleum jelly is put around the edges of the cover slips, the slides
can be kept for several days.
Hazards / Precautions - The stain used can stain skin and clothes.
The fixative solution is flammable. Avoid contact with and breathing of
any of the chemicals used to kill the insects.
Materials & Equipment
Needs to top
Materials needed for lab:
Buds from a variety of pollen producing flowering plants (such as beans,
spiderworts and lilies)
Microscope slides and overspills
A probe and scalpel or razor blade
A compound microscope capable of at least 400X magnification
A Bunsen burner or hot plate
Acetocarmine stain. Most biological supply companies carry prepared
acetocarmine that is ready to use.
3:1 fixative consisting of 3 parts 100% ethanol and 1 part glacial acetic
acid. (600 ml ethanol and 200 ml glacial acetic acid). 100% methanol
can be used in place of the ethanol.
Testes from grasshoppers, crickets and other insects
Previous practice in using compound microscopes and preparing slides
Students should be able to identify the cells undergoing meiosis.
The Student Lab to
Collection of plant buds
for the meiosis lab:
It is a good idea to plan ahead and gather
flower buds when they are available, especially in the spring. It
is important that the buds are very young, preferably before the production
of pollen. Any species of pollen producing flower will do.
Lilies, spiderworts and beans work well because they are easy to find and
have large chromosomes that stain well. Otherwise, greenhouses and
florist shops are good sources of flower buds throughout the year.
Try to pick young inflorescences with series of intact flower buds. To
preserve the buds, first carefully remove the buds from the plants. Put
the buds in containers that can be stoppered and stored easily. Add
enough (3:1 ethanol/acetic acid) fixative to each container to insure that
the buds stay covered. This lab can be done at any time of the year
if the materials are collected and preserved beforehand. If you are
using freshly picked buds, you need to store them in the fixative solution
for at least several days before the lab. The fixative will bleach
out pigments such as chlorophyll in the bud that can interfere with the
staining process. They can be stored for over a year.
Collection of animals testes
for the meiosis lab:
Collect the insects you plan on using in the
late spring and early summer when the male insects are producing sperm.
Grasshoppers are common insects that are easy to catch, have testes that
are easy to locate and breed in the late spring while school is still in
progress. House crickets may be a good source of specimens, too.
Consult a zoology or entomology text so you can distinguish between male
and female insects. Put the insects in a killing jar and add a chemical
such as dichlorobenzene or ethyl acetate to kill the insect. Finger
nail polish remover or moth balls will work too. Once the male insects
are dead, remove the testes from the insects and store them in the fixative
solution (3:1 ethanol / acetic acid). Directions for excising
and preserving the testes are included in most invertebrate and microtechniques
lab books. I have included a frontal section diagram of the posterior
of a male grasshopper in case, an appropriate text can not be located.
The shape of the internal organs will vary between species of grasshoppers.
They can be stored for over a year in fixative.
for Preparation of Plant and Animal Meiosis Slides:
Remove the bud from the fixative and place
it in a open flat container (petri plates work well). Use an eye
dropper to add some of the fixative to the bud so the bud doesn't dry out.
The container should be open so the you can use pointed forceps to dissect
out the anthers. Use a dissecting microscope if you need to.
Good lighting and manual dexterity are helpful. Check a diagram
in any good botany book for the location and shape of the anthers in a
typical plant bud. Once the anthers have been isolated, transfer
them to a slide and cover the anthers with acetocarmine stain. Use
a probe or razor blade to mash up the anthers in the acetocarmine stain.
Use a fine tipped forceps to remove debris such as anther walls.
Make sure that you have removed the outside of the anthers. Let the
remainder of the anthers set in the stain for several minutes. Add
more acetocarmine stain to the slide if dries out. Cover the
anther remainders on the slide with a cover slip. Check the heating
directions and squash technique that is used for both plant and animal
Remove the testis from the fixative and place
it in slide. Use forceps or a razor blade to smash and smear the
contents of the testis over the central part of the slide. Remove
any large pieces of debris with fine pointed forceps. Use an eye
dropper to cover the material with acetocarmine stain. Let the material
set in the stain for at least several minutes. Add more acetocarmine
stain to the slide if dries out. Cover the testis material
on the slide with a cover slip.
Heating to set the stain and
the squash technique:
The next step is heating the slide gently.
If a Bunsen burner or alcohol lamp is used, hold the end of the slide and
move it back and forth through the flame. You have to be careful
not to heat the slide so the stain boils or burn your fingers. Gentle
heating will improve the staining process considerably. Take your
time. If you heat the slide on a hot plate, it has to be set at 80
degrees C. Allow the slide to set on the hot plate for 3 - 5 minutes.
Make sure the stain on the slide does not boil. If the material starts
to dry out add more stain to the edge of the oversleep. Capillary
action will pull it in. After heating the slide, let it cool
for a few seconds. Place the slide between layers of paper towels
or napkins. Press straight down firmly. You need to be
careful not to break the slide. This squashing process flattens the
cell's nuclei and spreads out the chromosomes. The excess stain that
leaks out will absorbed by the towels.
Examination of the Slides:
The slides are now ready to be examined using
a compound microscope. With hard work, you might find meiotic cells.
Remember that you may have to look through quite a few slides to locate
cells in different stages of meiosis. Having diagrams or photos of
meiotic cells as reference points is quite useful in the process of searching
the slides. Remember, that you may search quite a few slides before
you get lucky. If you find a slide you want to keep for several days,
adding petroleum jelly to the edge of the cover slip will prevent it from
Methods of Evaluation/Assessment
Because of the level of microscope skills and time involved,
the lab should be used for enrichment or independent projects for advanced
Additional Ideas / Trouble
Shooting Hints to
Trouble Shooting Suggestions:
1. Allow the slides to set in the acetocarmine stain for at least
2 - 3 minutes or longer if the cells are not stained so you can see the
2. The slides must be heated properly to set the stain. Do
not let them boil or dry out.
3. The specimens must be squashed to flatten the material so nuclei
can be seen.
4. This technique requires patience and practice. Making 7
to 10 slides each time increases your chances of locating cells undergoing
5. Have backup meiosis slides from a biological supply house so students
can see what they are looking for.
6. Have the students study diagrams of cells under going both mitosis and
meiosis, so they can tell the difference.
7. The anthers and testes have to be collected at the right time of the
year in your area to ensure that meiosis is occurring.
8. Different plants and animals could be used to prepare meiosis slides.
Lilies, spiderworts and beans are good choices for plant slides due to
their availability, anther size and large chromosomes. Grasshoppers
and crickets are easily found and make good choices for animal slides.
References Including Web Addresses
Galigher, Albert & Kozloff, Eugene. Essentials of Practical Microtechnique.
Lea and Febiger Publishing, Philadelphia, 1971.
This is an older text, but a great resource for preparing slides.