Linkage, Crossing Over & Sex-linked Inheritance Practice Set: NEB 12 Biology

Worked practice

Build the result from meaning, not memory

Linked genes occupy the same chromosome and may be inherited together; crossing over between homologous nonsister chromatids creates recombinants, while sex-linked genes follow sex-chromosome transmission.

The governing relationship is Recombination frequency=recombinant offspring/total offspring×100%; values below 50% can estimate map distance in centimorgans for nearby genes. Check the convention, geometry or boundary condition before calculation.

Independent practice ladder

1. Define the key physical quantities and give their SI units.
2. Draw and label the relevant wave, ray, mode or energy diagram.
3. Recalculate the worked example after changing one input by a factor of two.
4. Explain the result without equations.
5. Create a Nepal-relevant situation such as a classroom speaker, musical pipe, optical slit or thermal machine.
6. Compare two cases and predict the larger output before calculating.
7. Find and repair one deliberately wrong sign, node or unit.
8. Write a three-mark answer and a five-mark answer.

Answer protocol: diagram → known data → principle → symbolic equation → SI substitution → result → physical check. Calling genes on one chromosome completely inseparable, exceeding 50% recombination, or applying autosomal ratios to X-linked crosses.

NEB answer method

Model → evidence → equation → check

First identify the system and what the question asks. Label the diagram, apparatus or reaction with SI quantities, then state the principle before selecting an equation. Solve symbolically where possible and check units, limiting cases and chemical or physical meaning.

Make the idea concrete in Nepal

Connect the model to a school laboratory, household technology, health, environment, energy or local material. The example should clarify the science rather than merely mention a place. Compare a prediction with an observation and record uncertainty.

Review the NEB Class 12 Biology revision roadmap and the complete Biology guide. For online or physical tuition, call 9846662070.

Frequently asked questions

Questions students ask about Linkage, Crossing Over and Sex-linked Inheritance

References and next steps

Scope checked against CDC Nepal; concept support from an institutional reference and OpenStax Science. Continue with the Linkage, Crossing Over and Sex-linked Inheritance cluster.