Instructions
A Punnett square, devised by the British geneticist Reginald Punnett, can be drawn that applies the rules of probability to predict the possible outcomes of a genetic cross or mating and their expected frequencies. To prepare a Punnett square, all possible combinations of the parental alleles are listed along the top (for one parent) and side (for the other parent) of a grid, representing their meiotic segregation into haploid gametes. Then the combinations of egg and sperm are made in the boxes in the table to show which alleles are combining. Each box then represents the diploid genotype of a zygote, or fertilized egg, that could result from this mating. Because each possibility is equally likely, genotypic ratios can be determined from a Punnett square.
After reading the chapter and viewing the video, use a punnett square to plot out at least 2 traits within your own family ( eye color, ear lobe location) or any other trait that you find interesting..Please explain your findings
As you noted, a Punnett square is a diagram used to predict the possible genotypes of offspring resulting from the genetic cross or mating of two parents (Punnett, 1905). To construct one, all possible combinations of the parental alleles are listed along the top and side of a grid. Where the rows and columns intersect, the alleles combine to show the potential genotypes of the offspring (Harris & Huxley, 2012). This allows for easy visualization of Mendel’s laws of segregation and independent assortment.
Let me share two examples using Punnett squares from my own family. First, eye color. My mother has brown eyes (genotype BB or Bb) and my father has blue eyes (genotype bb). A Punnett square predicting their offspring would be:
B b
B Bb Bb
b Bb bb
As seen, there are three possible genotypes for their children – two combinations for brown eyes (BB and Bb) and one for blue eyes (bb). My sister indeed has blue eyes, matching the bb prediction.
A second example is earlobe attachment. My paternal grandmother’s earlobes were free-hanging (ee genotype) while my grandfather’s were attached (E_). Their Punnett square is:
E e
E Ee Ee
e Ee ee
Both my father and his sibling have attached earlobes, consistent with the Ee genotype. No one in that generation had fully free earlobes, as expected from the square.
In summary, Punnett squares provide a straightforward way to predict inheritance patterns of traits by visualizing the combinations of parental alleles. The examples from my family corroborate the predictions made using this classic genetic tool.
Harris, H., & Huxley, J. S. (2012). Genetics. In Encyclopædia Britannica. Encyclopædia Britannica. https://www.britannica.com/science/genetics
Punnett, R. C. (1905). Mendelism. London: Macmillan.
