Polyploidy

Japanese: 倍数性 - ばいすうせい

A phenomenon in which differences in the number of chromosomes are observed between individuals of the same or similar species. The number of chromosomes is determined by species, and if the number in reproductive cells is the basic number (represented by n), then somatic cells usually contain twice that number (2n), which is called diploidy. Some wild plants have several times the basic number of chromosomes. For example, the number of chromosomes in einkorn is 14 (2n), but durum wheat and bread wheat have 28 and 42 chromosomes, respectively, which are four and six times the basic number of chromosomes in einkorn, so they are called tetraploid and hexaploid. The emergence of polyploids is thought to have played a major role in the evolution of species. When the number of chromosomes in an organism is an integer multiple of the basic number, it is called whole polyploidy, and when only some chromosomes are increased or decreased, it is called aneuploidy. Polyploidy can also be artificially created for breeding purposes, and colchicine is a well-known chromosome doubling agent.
→ Related topics Genome | Mutation

Source : Heibonsha Encyclopedia About MyPedia Information

Japanese:

同種あるいは近い種の個体間で，染色体数に倍数関係の違いが見られる現象。染色体の数は種によって決まっており，生殖細胞におけるものを基本数（nで表す）とすると，体細胞にはその倍（2n）含まれるのが普通であり，これを二倍体と呼ぶ。野生植物のなかに基本数の数倍の染色体をもつものがある。たとえば一粒コムギの染色体数（2n）は14であるが，マカロニコムギ，パンコムギはそれぞれ，28，42で，一粒コムギの基本数の４倍，６倍の染色体をもつので，四倍体，六倍体と呼ばれる。倍数体の出現は種の進化にとって大きな役割を果たしてきたと考えられている。ある生物の染色体数が基本数の整数倍のときを整倍数性，一部の染色体のみに増減があるときを異数性という。倍数性は品種改良のために人工的に作ることも行われ，コルヒチンは染色体倍加剤として有名。
→関連項目ゲノム｜突然変異

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