Question

Recalling the Law of Independent Assortment
Explain how corn can be used as an example of Mendel's law of independent assortment.

Answer 1

Mendel’s Law of Independent Assortment says that alleles of different genes segregate into gametes independently of one another (provided the genes are on different chromosomes or far apart on the same chromosome). Corn (maize) is a classic and convenient organism to demonstrate this.

Example using two corn traits
- Choose two independently assorting genes, e.g.:
- A = yellow kernels (dominant) vs a = white kernels (recessive)
- B = smooth (starchy) kernels (dominant) vs b = wrinkled (recessive)
- Cross two true‑breeding parents: AA BB (yellow, smooth) × aa bb (white, wrinkled).
- All F1 offspring are Aa Bb (yellow, smooth).
- When F1 plants self-fertilize, each Aa Bb plant produces four types of gametes with equal frequency by independent assortment: AB, Ab, aB, ab.
- A dihybrid Punnett square predicts the F2 phenotypic ratio:
- 9/16 yellow & smooth (A_ B_)
- 3/16 yellow & wrinkled (A_ bb)
- 3/16 white & smooth (aa B_)
- 1/16 white & wrinkled (aa bb)

Why corn is especially useful experimentally
- Each kernel on an ear is the product of an independent fertilization, so one ear yields many offspring to score.
- Kernel phenotypes (color, texture) are easy to see and count, so you can directly observe expected 9:3:3:1 segregation on a single ear.
- If two traits do not show the 9:3:3:1 ratio, that suggests the genes are linked (on the same chromosome) and recombine less often — maize was historically important for mapping such linkages.

This visual, high‑replicate F2 segregation of independent traits in corn provides a clear demonstration of Mendel’s Law of Independent Assortment.