Advanced Placement (AP) Biology Practice Exam

What does diploid mean in terms of chromosomes?

1. One set of chromosomes

2. Two sets of unpaired chromosomes

3. Two sets of chromosomes

4. Single set of paired chromosomes

The correct answer is: Two sets of chromosomes

The term "diploid" refers to a cell or organism that has two complete sets of chromosomes. In humans and many other organisms, these two sets include one set inherited from each parent. This configuration allows for a diverse combination of genetic information, which is essential for sexual reproduction and contributes to genetic variation in a population. For instance, in humans, the diploid number of chromosomes is 46, organized into 23 pairs. Each pair comprises one chromosome from the mother and one from the father, representing the genetic contribution from both parents. This diploid state contrasts with haploid cells, which contain only a single set of unpaired chromosomes, typically seen in gametes like sperm and egg cells. The other options do not accurately describe the diploid state: having one set of chromosomes would be haploid, two sets of unpaired chromosomes misrepresents the paired nature of diploid cells, and a single set of paired chromosomes describes a monophyletic structure rather than the diploid state. Thus, the correct understanding of diploid is two complete sets of chromosomes, which is fundamental in concepts such as meiosis and genetic inheritance.