Diploid

Diploid describes a cell or organism that has two complete sets of chromosomes. In a diploid cell, chromosomes are in pairs - one set inherited from each parent. For example, human somatic cells are diploid with 46 chromosomes (23 pairs).

• We often denote the diploid number as 2n. For humans, 2n = 46. This means n (the number of unique chromosomes) is 23, and having two sets (2x23) gives 46 total.
• Nearly all cells in the human body (except gametes) are diploid. Having two sets of each chromosome also means having two copies of each gene (which can be the same allele or different alleles).
• Diploid organisms produce haploid gametes through meiosis. When two haploid gametes fuse at fertilization, the diploid number is restored in the offspring.

• Common question: "How many chromosomes are in a human [or given organism] diploid cell?" For humans, recognize the answer is 46 (in 23 pairs).
• Be careful with terminology: an exam might say "2n = 14 for a certain species" - that indicates diploid cells have 14 chromosomes total. You should then know n = 7 (haploid number).