The memory device for figuring out the combinations a heterozygous parent can produce for two traits is called the Punnett Square.

Here's how it works:

1. Set up the square: Draw a 2x2 grid.

2. Label the top and side: Each square represents a possible combination of alleles. Label the top row with the alleles for one trait from the parent, and the side column with the alleles for the other trait from the same parent.

3. Fill in the squares: For each square, combine the allele from the top row with the allele from the side column.

4. Interpret the results: The Punnett Square shows you all the possible combinations of alleles that the offspring could inherit, and their probabilities.

For example, let's say a parent is heterozygous for both hair color (B = brown, b = blonde) and eye color (E = brown, e = blue). The Punnett Square would look like this:

| | BE | Be |

|--------|------|------|

| bE | BbEE | BbEe |

| be | bbEE | bbEe |

This shows us that this parent could produce offspring with four different combinations of alleles:

* BbEE: Brown hair, brown eyes

* BbEe: Brown hair, brown eyes

* bbEE: Blonde hair, brown eyes

* bbEe: Blonde hair, brown eyes

The Punnett Square is a simple but powerful tool for understanding Mendelian genetics.