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9700 A Level Biology/Topic 16 Inheritance/7 interactive simulations/drag to rotate the 3D models

Inheritance, made interactive

Seven 3D simulations covering Topic 16.1 Passage of information from parents to offspring, 16.2 The roles of genes in determining the phenotype and 16.3 Gene control. Step through meiosis, make recombinant chromatids, build dihybrid crosses, run a chi-squared test, connect genes to phenotypes and switch genes on and off.

1. The stages of meiosis 3D · 16.1

Meiosis is a reduction division: a diploid cell (2n) makes four haploid (n) cells. This cell has two homologous pairs. Step through the eight stages.

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Stage

STAGE
CELLS

2. Sources of genetic variation 3D · 16.1

Crossing over, independent assortment and random fertilisation all make offspring genetically different. Make a chiasma, then count the possible combinations.

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Process

GAMETE COMBINATIONS (2ⁿ)
ZYGOTE COMBINATIONS

3. Dihybrid crosses, linkage and epistasis 3D · 16.2

Two genes at once. Cross two heterozygous pea plants for seed shape and colour, then see how linkage and epistasis change the ratio.

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Cross

PHENOTYPE RATIO

4. The chi-squared test 3D · 16.2

Grow F2 offspring from a dihybrid cross and test whether the observed numbers fit the expected 9 : 3 : 3 : 1 ratio.

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Data

phenotypeOE(O−E)²/E

5. Genes, proteins and phenotype 3D · 16.2

A gene codes for a protein; a faulty allele can make a faulty protein and a different phenotype. Compare the normal and mutant versions.

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Gene

6. The lac operon 3D · 16.3

In E. coli, the enzymes to use lactose are made only when lactose is present. Add and remove lactose and watch the repressor.

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Medium

REPRESSOR
β-GALACTOSIDASE

7. Gibberellin, DELLA and transcription factors 3D · 16.2-16.3

The Le allele codes for an enzyme that makes active gibberellin; the le allele does not. Gibberellin switches on growth genes by removing DELLA repressor proteins.

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Genotype

Built for Cambridge AS & A Level Biology 9700, Topic 16 (A Level). Models are simplified and not to scale; random results differ each run.

About this lab: Inheritance

Seven interactive 3D simulations for Cambridge A Level Biology 9700 topic 16 Inheritance: the eight stages of meiosis in animal and plant cells, crossing over, independent assortment and random fertilisation, dihybrid crosses with test crosses, autosomal linkage and epistasis, the chi-squared test, genes, proteins and phenotypes for TYR, HBB, F8 and HTT, the lac operon, and gibberellin with the Le and le alleles and DELLA proteins.

Seven 3D simulations covering Topic 16.1 Passage of information from parents to offspring, 16.2 The roles of genes in determining the phenotype and 16.3 Gene control. Step through meiosis, make recombinant chromatids, build dihybrid crosses, run a chi-squared test, connect genes to phenotypes and switch genes on and off.

Inheritance is a free, browser-based simulation for Cambridge International AS & A Level Biology 9700 (topic 16 Inheritance). The course is assessed in Paper 1 (Multiple choice), Paper 2 (AS structured), Paper 3 (Advanced practical), Paper 4 (A Level structured), Paper 5 (Planning, analysis, evaluation). Syllabus for examination in 2025-2027. There are 7 tabs, each a self-contained experiment with its own controls and live readings, and nothing to install: it runs on a laptop, tablet or classroom projector.

Syllabus coverage

Full syllabus map: A Level Biology 9700 topic 16.

How to use this simulation

  1. 1. The stages of meiosis. Meiosis is a reduction division: a diploid cell (2n) makes four haploid (n) cells.
  2. 2. Sources of genetic variation. Crossing over, independent assortment and random fertilisation all make offspring genetically different.
  3. 3. Dihybrid crosses, linkage and epistasis. Two genes at once.
  4. 4. The chi-squared test. Grow F2 offspring from a dihybrid cross and test whether the observed numbers fit the expected 9 : 3 : 3 : 1 ratio.
  5. 5. Genes, proteins and phenotype. A gene codes for a protein; a faulty allele can make a faulty protein and a different phenotype.
  6. 6. The lac operon. In E.
  7. 7. Gibberellin, DELLA and transcription factors. The Le allele codes for an enzyme that makes active gibberellin; the le allele does not.
  8. The buttons at the end of the tab strip give the scene the whole window (Full screen, Hide controls) and, on a dark stage, a projector-friendly palette (Light scene). Many scenes also have drag handles: drag them to change the set-up directly.

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