Final answer:
The average percentage of loci that are heterozygous can be found by assessing a tetrahybrid cross. The expected proportion of offspring with the dominant phenotype for all four loci is 81/256, as calculated using sum and product rules in genetics.
Step-by-step explanation:
The average percentage of loci that are heterozygous refers to the expected proportion of genes in a genome where the two alleles are different, one inherited from each parent. In genetics, when discussing genotypic proportions in a population or in offspring from a particular cross, the term "heterozygosity" is used to describe this scenario. Here, we are examining a tetrahybrid cross, focusing on the dominant phenotype at four different loci (A, B, C, D). The expected proportion of offspring that exhibit the dominant phenotype for all four loci is calculated using the sum and product rules. Specifically, for each gene, the probability that an offspring is either homozygous dominant or heterozygous (which still results in the dominant phenotype) is 3/4, as it's the sum of 1/4 for homozygous dominant and 1/2 for heterozygous. Therefore, the overall probability of an offspring being dominant for all four loci is 3/4 x 3/4 x 3/4 x 3/4, which is 81/256.