- 1). Draw a grid with six squares.
- 2). Place the traits of one parent on the top middle and right squares and the traits of another parent on the left middle and bottom squares. For example, a punnet square showing two parents with the traits Tt and TT would have a "T" in the top middle square, a "t" in the top right square, a "T" in the left middle square, and a "T" in the left bottom square.
- 3). Fill in the remaining four squares with the one letter from both the top row and one letter from the left row. For example, a Punnett square with two parents whose traits are Tt and TT, the middle row's middle square would have "TT" (T + T =TT), the middle row's right square would have "Tt" ( t + T = Tt), the bottom row's middle square would have "TT" and the bottom right square would have "Tt".
- 4). Determine the probability of an offspring's traits by taking the number of times a certain set of traits is present over the sum of the total amount of offspring. For example, in a Punnett square showing two parents with the traits Tt and TT, the probability of an offspring with the trait set of TT or Tt would be 2:4 (written as 2/4) while the probability of an offspring with the trait of tt would be 0:4.
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