Researchers studying a small milkweed population note that some plants produce a toxin and other plants do not. They identify the gene responsible for toxin production. One allele (t1) codes for an enzyme that makes the toxin, and another allele (t2) codes for a nonfunctional enzyme that cannot produce the toxin. Heterozygotes produce an intermediate amount of toxin. The genotypes of a random sample of 200 individuals in the population were identified as shown in the table.