IB Biology HL 2.3.11 Crossing over, chiasmata and variation Question Bank
Practise IB Biology HL 2.3.11 by analysing crossing over and meiosis mechanisms that generate genetic variation.
- Syllabus
- First assessment 2025
- Course
- Biology HL
- Level
- HL
Practise IB Biology HL 2.3.11 by analysing crossing over and meiosis mechanisms that generate genetic variation.
Hemophilia is a sex-linked disease that affected some members of royal families in Europe during the 19th and 20th centuries.

The diagram shows the structure of two chromosomes after the first division of meiosis, assuming that there was no crossing over or chiasmata formation.

Draw the same chromosomes to show their structure at the same stage of meiosis if there had been one chiasma between two gene loci.
All four upper arms with one A and both chromosomes with one B and one b on the lower arms.

official chromosome answer
The chromatids can be shown as single lines rather than the wider versions in the question.
State the stage of meiosis where chiasmata formation may occur.
prophase I;