A Punnett square is a 2×2 grid that predicts the offspring of a single-gene cross. It's the breeder's back-of-the-napkin math, and it explains why you see what you see in the tent.

The 3:1 ratio

Cross two heterozygotes (Aa × Aa) — say, two plants both carrying one purple allele and one green allele. Their seeds split:

AA (purple/purple)
25%
homozygous dominant
Aa (purple/green)
50%
heterozygous
aa (green/green)
25%
homozygous recessive

Three out of four offspring show the dominant trait. One in four shows the recessive trait. That's the 3:1 ratio, and it's why you're never quite sure which seedling is going to surprise you.

Apply this to your hunt

  • If you want to lock in a recessive trait, you need both parents homozygous (aa × aa). Every seed will show it.
  • If you want to *hide* a recessive trait in a stable, you can cross a known carrier (Aa) into a homozygous dominant (AA). The trait will disappear visually but stay in the gene pool — useful for a surprise comeback later.