How do you find the phenotypic ratio in a monohybrid genetic cross?

Question

for example Dominant:recessive or Recessive:Dominant, ETC.

Answer 1

Do the cross using a Punnett square.
Then count up the results in the boxes of the Punnett square.
When you write the results in the form of a "score" or ratio, you have the phenotype ratio.

Example: B = Black b = albino

Parents Bb x Bb

Side of Punnett square has gametes B and b from first parent.
Above Punnett square has gametes B and b from second parent.

First row of Punnett square says BB Bb.
Second row of the square says bB bb.

The ratio is 3 black: 1 albino.