Diploid Topics

• chromosome pairs
• diploid zygote
• diploid organisms
• germ cells
• somatic fusion
• number of chromosomes
• haploid cells
• diploid cells
• sex cells
• common wheat
• haploid gametes
• somatic cells
• haploid number
• polyploidy
• gamete
• aureus
• sperm
• allopolyploid
• mammals
• organism

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Diploid, Diploid

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In humans, the somatic cells that compose the body are diploid (containing two complete sets of chromosomes, one set derived from each parent), but sex cells (sperm and egg) are haploid. In contrast, tetraploidy (four sets of chromosomes) is a type of polyploidy and is common in plants, and not uncommon in amphibians, reptiles, and various species of insects.

The haploid number (n) is the number of chromosomes in a gamete of an individual. Both of these numbers apply to every cell of a given organism. For humans, x = n = 23; a diploid human cell contains 46 chromosomes: 2 complete haploid sets, or 23 homologous chromosome pairs. In some species (especially plants), x and n differ, for example common wheat is an allopolyploid with six sets of chromosomes, two sets coming originally from each of three different species, with six sets of chromosomes in most cells and three sets of chromosomes in the gametes.

Gametes (germ cells, sex cells, sperm, and ova) are haploid cells. The haploid gametes produced by (most) diploid organisms are monoploid, and these can combine to form a diploid zygote, for example most animals are diploid and produce monoploid gametes.

Nearly all mammals are diploid organisms (the viscacha rats Pipanacoctomys aureus and Tympanoctomys barrerae are the only known exceptions as of 2004), although all individuals have some small fraction of cells that display polyploidy. Human diploid cells have 46 chromosomes and human haploid gametes (egg and sperm) have 23 chromosomes.

There are two types: diploid-triploid mixoploidy, in which some cells have 46 chromosomes and some have 69, and diploid-tetraploid mixoploidy, in which some cells have 46 and some have 92 chromosomes.

Tetraploids can be reconstituted from the diploids, for example by somatic fusion.

Source: Wikipedia > Ploidy#diploid