GCSE Biology (AQA)

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Drawing Punnett Squares

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Inheritance, Variation and Evolution Reproduction

Drawing Punnett Squares

1:17 Genetic Crosses and Family Trees
Spec 4.6.1.6
Previous DNA Base Pairing Next Family Trees
  • Punnet square diagrams can be drawn using a ruler and a pen or pencil.
  • Constructing Punnet squares allows for predictions about the probability of different genetic outcomes.
  • Essential tools for drawing a Punnet square include a ruler, pen, or pencil.
  • Begin by drawing a square grid that is three boxes long and three boxes wide, suitable for a simple genetic cross.
  • This type of diagram is known as a Punnett square in GCSE biology, named after Reginald Punnett.
  • Write the genotypes of the parents on the diagram, with one parent's genotype along the top and the other's down the side.
  • Dominant alleles are represented by an uppercase letter and are written first in any allele combination.
  • After setting up the genotypes, combine the rows and columns to fill in the square.
  • Interpret the results of the genetic cross, which in the example includes one homozygous dominant, one homozygous recessive, and two heterozygous outcomes.

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