diploïd

Diploid refers to a cell or organism that possesses two complete sets of chromosomes, one inherited from each parent. This condition is fundamental to the sexual reproduction cycle in many organisms, including most animals, plants, and fungi. The term originates from the Greek words di- (meaning "two") and -ploid (referring to sets of chromosomes).

In diploid organisms, the chromosome number is denoted as 2n, where n represents the haploid number—the number of unique chromosomes in a gamete (sperm or egg). For example, humans have a diploid chromosome count of 46 (2n = 46), consisting of 23 pairs of homologous chromosomes. One set of chromosomes is derived from the mother, and the other from the father, ensuring genetic diversity through recombination during meiosis.

Diploidy provides several evolutionary advantages, such as genetic stability through redundancy and the ability to mask recessive mutations. However, it also introduces mechanisms like Mendelian inheritance, where traits are passed in predictable patterns. Some organisms, such as humans, maintain diploidy throughout most of their life cycle, except for gametes, which are haploid (n).

Diploidy contrasts with haploidy, where organisms have a single set of chromosomes, and polyploidy, where multiple sets exist. While diploidy is common in eukaryotes, some organisms, like certain algae or fungi, exhibit alternation of generations, switching between diploid and haploid phases during their life cycle. This distinction is crucial in genetics, evolution, and developmental biology, influencing traits, reproduction, and species diversity.