Look for a reduction division
In an unfamiliar life cycle, meiosis can be recognised by looking for a change from a diploid chromosome number to a haploid chromosome number.
Meiosis is a reduction division. During the first meiotic division, homologous chromosomes separate, reducing the chromosome number by half.
If a life-cycle diagram shows cells changing from 2n to n, meiosis has occurred across that part of the life cycle.
diploid (2n) → meiosis → haploid (n)
Using chromosome number in an unfamiliar diagram
- Identify the chromosome number or ploidy shown for each stage.
- Find where the chromosome number is reduced by half.
- Identify this transition as meiosis.
Exam Tip: In an unfamiliar life cycle, look for the point where the chromosome number changes from diploid to haploid. That reduction identifies where meiosis has occurred.