Advanced Placement (AP) Biology Practice Exam

What is the outcome of meiosis in sexually reproducing organisms?

1. Cells with double the chromosome number

2. Cells with the same chromosome number

3. Cells with half the chromosome number

4. Cells with variable chromosome number

The correct answer is: Cells with half the chromosome number

The outcome of meiosis in sexually reproducing organisms is the production of cells with half the chromosome number. Meiosis is a specialized form of cell division that reduces the chromosome number by half, resulting in haploid cells from an initial diploid cell. This is crucial for sexual reproduction because it ensures that when two gametes fuse during fertilization, the resulting offspring will have the appropriate diploid chromosome number. In the first stage of meiosis, homologous chromosomes are paired and then separated into different cells, going through two rounds of division (meiosis I and meiosis II). As a result, each of the four daughter cells produced at the end of meiosis contains only one set of chromosomes, or half the original number. This halving of chromosomes is essential for maintaining the stability of the species' chromosome number across generations when gametes unite.