Which of the following definitions best describes the concept of ploidy?

Ploidy refers specifically to the number of sets of chromosomes present in a cell. In eukaryotic organisms, cells can have different ploidy levels, such as diploid (two sets of chromosomes), haploid (one set), triploid (three sets), and so on. This concept is fundamental in genetics because it influences how genetic information is inherited and expressed.

Understanding ploidy is essential for studying various biological processes, such as meiosis and fertilization, where the chromosome number changes and contributes to genetic diversity through recombination and segregation. Knowledge of ploidy is also critical in fields like agriculture and horticulture, where polyploid plants can exhibit traits such as increased size or resilience.

Other definitions do not accurately capture the essence of ploidy. The total number of genes, the variety of alleles, and an individual's genetic makeup pertain more to the genetic composition but do not address the foundational concept of chromosome sets that defines ploidy.