Biology STAAR (State of Texas Assessments of Academic Readiness) Practice Test

What is the purpose of a Punnett square in genetics?

1. To determine the exact phenotype of an organism

2. To predict the possible genotypes and phenotypes of an organism

3. To analyze the mutation rates in a gene

4. To illustrate the process of cellular division

The correct answer is: To predict the possible genotypes and phenotypes of an organism

The purpose of a Punnett square in genetics is to predict the possible genotypes and phenotypes of an organism as a result of genetic crosses between parents. This tool visually represents the combinations of alleles that can occur when gametes (sperm and egg cells) combine during fertilization. By organizing the alleles from each parent in a grid format, a Punnett square allows researchers and students to foresee potential genetic outcomes, providing a clearer understanding of inheritance patterns. For example, if each parent is heterozygous for a trait (e.g., one allele for brown eyes and one for blue eyes), the Punnett square will show the probability of their offspring inheriting each combination of traits. This tool is particularly useful when studying Mendelian genetics, where traits are controlled by single genes with dominant and recessive alleles. Understanding these patterns can help in various applications, such as predicting genetic diseases or plant breeding outcomes. The other options refer to distinct concepts in genetics and biology that do not align with the primary function of the Punnett square. Determining exact phenotypes pertains to a more detailed analysis beyond the initial predictions provided by the Punnett square, mutation rates focus on genetic alterations rather than inheritance predictions, and cellular division illustrates a different