Fish Stripes and Punnett Squares

How can we use our knowledge of genetics to predict genotypes and phenotypes?

By identifying parental genotypes and applying Mendel’s laws to predict offspring outcomes using Punnett squares.

If you know the genotype of the parents, how would you go about predicting the genotype and phenotype of all possible offspring?

 List all possible gametes from each parent and fill in a Punnett square to show every combination of alleles.

If you know the phenotype of the offspring, how do you go about predicting the phenotype/genotype of the parents?

Work backward using the offspring ratios – for example, a 3:1 ratio suggests both parents are heterozygous.

How would you determine the probability of obtaining certain genotypes and phenotypes?

Use ratios from Punnett squares (e.g., ¼ RR, ½ Rr, ¼ rr → 3 purple : 1 white for a dominant trait).

What is a Punnett square?

A diagram that shows all possible allele combinations from parental gametes and their expected ratios in offspring.

How would you explain all the parts of a Punnett square?

Columns = alleles from one parent; rows = alleles from the other parent; boxes = possible offspring genotypes.

How can you use it to predict the chances of getting offspring with different combinations of alleles for a single gene?

Fill the Punnett square and count how many boxes show each genotype; the frequency equals the probability of that genotype.

You are encouraged to practice using slot machines and Punnett Squares to make predictions about the probability of inheriting certain genes and traits.

Practice strengthens understanding of random assortment and inheritance probabilities.