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(genetics) The state of being polyploid, that is more than two sets of the chromosomes in a nucleus


Ploidy refers to the number of sets of homologous chromosomes in the genome of a cell or an organism. Each set is designated by n. Thus, the term diploidy would refer to a state of being diploid, that is having two sets of the chromosomes (and therefore two copies of genes), especially in somatic cells. A diploid is a cell or an organism having two sets of homologous chromosomes and is represented by 2n. There are certain plants and animals that have more than two sets of chromosomes in the nucleus of a somatic cell. When there are multiple sets of chromosomes, the state is referred to as polyploidy. Polyploidy has many types based on the number of chromosome sets in the nucleus. These types are as follows:

  • Triploid - with three sets, e.g. seedless watermelons
  • Tetraploid - with four sets, e.g. Salmonidae fish
  • Pentaploid – with five sets, e.g. Kenai Birch (Betula papyrifera var. kenaica)
  • Hexaploid – with six sets, e.g. wheat, kiwifruit
  • Heptaploid (or septaploid) – with seven sets
  • Octaploid (or octoploid) – with eight sets, e.g. dahlias
  • Decaploid – with ten sets, e.g. certain strawberries
  • Dodecaploid – with twelve sets, e.g. plant species Celosia argentea, amphibian species Xenopus ruwenzoriensis

Word origin: from Greek diplous, double


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