9. In a Punnett square, what do the letters represent? A) Different types of cells B) Possible phenotypes C) Alleles for a particular gene D) Chromosomes

## Step 1<br />A Punnett square is a graphical representation used in genetics to predict the genotypes of a particular cross or breeding experiment. It is named after Reginald C. Punnett, who devised the approach.<br /><br />## Step 2<br />The letters in a Punnett square represent alleles for a particular gene. Alleles are different forms of a gene that can exist at a specific locus on a chromosome.<br /><br />## Step 3<br />Each parent contributes one allele for each gene to their offspring. The Punnett square is used to determine the probability of an offspring having a particular genotype.<br /><br />## Step 4<br />The other options provided are not accurate descriptions of what the letters in a Punnett square represent. For instance, chromosomes are structures within cells that contain a person's genes, but they are not represented by the letters in a Punnett square. Similarly, phenotypes are the observable characteristics or traits of an organism, and they are determined by the combination of alleles an organism has, but they are not represented by the letters in a Punnett square.