Biology 11–12 · Year 12
Mitosis in an onion root tip squash and the mitotic index
Module 5: Heredity (Cell Replication)
Teacher-led demonstration
A teacher carries out this activity as a demonstration. Its materials, steps, variables, misconceptions and sources are not published on the open web, and neither is any result, control or note that states a number or an amount: tutors and administrators read them on the learning platform, with the safety card first. The idea, the hazards and the curriculum references are below.
Open the procedure on the learning platform (tutor or administrator sign-in)
School laboratory, not for home
In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.
The idea
Growing root tips are full of dividing cells, and a stained squash shows every stage of mitosis at once so the fraction of cells dividing can be counted.
Safety card
Setting: In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.
Hazards
- Hot 1 mol/L hydrochloric acid: harmful to eyes and hot enough to scald
- Ethanoic alcohol fixative: flammable and corrosive; ethano-orcein stain contains ethanoic acid and is corrosive to eyes
- Scalpels
Controls
- Goggles throughout, as the source requires; root tips moved with a mounted needle at the hot acid; rinse splashes
- Fixative kept capped and away from flames; staff mix and dispense it
- Carry scalpels on a tile; cut away from the body
Note
It states a number or an amount, which may be part of the method, so it is shown with the method to tutors and administrators on the learning platform.
What you should see
It states a number or an amount, which may be part of the method, so it is shown with the method to tutors and administrators on the learning platform.
Curriculum references
The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.
- Biology Stage 6 Syllabus (2017), current: Year 11 taught to the end of 2026 and Year 12 to Term 3 2027BIO12-12BIO11/12-4BIO11/12-5
- Biology 11–12 Syllabus (2025), Year 11 focus area Cells as the basis of life; new syllabus not yet taught: Year 11 from Term 1 2027, Year 12 from Term 4 2027BI-11-01
- Biology 11–12 Syllabus (2025), Year 11 Working scientifically; new syllabus not yet taught: Year 11 from Term 1 2027, Year 12 from Term 4 2027BI-11WS-04BI-11WS-05
- Australian Curriculum v9No Australian Curriculum v9 code is listed.