A symbolic representation of the shape, size, and number of chromosomes that appear during nuclear division in cells. Karyotype analysis, which examines the karyotype, can provide some insight into the lineage, classification, and phylogenetic relationships between organisms. For example, the karyotype of broad bean is written as (1) K(2n) = 12 = 2M + 2m + 8s, or (2) 2n = 12 = 2 sc A m + 6B st + 4C t . Equation (1) means that the number of chromosomes in a diploid 2n somatic cell is 12, with 2 large chromosomes, 2 medium chromosomes, and 8 small chromosomes. Equation (2) further shows the position of the centromere and secondary constriction, with m, st, and t indicating that the chromosomes are in the middle, subterminal, and terminal positions, respectively, and sc indicates the presence of a secondary constriction. Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information |
細胞の核分裂の際に現れる染色体の形,大きさ,数を記号でまとめて表示したもの。核型を調べる核型分析によって生物間の系統,分類や類縁関係をある程度知ることができる。核型を示すのに,たとえばソラマメでは,(1) K(2n)=12=2M+2m+8s とか,(2) 2n=12=2scAm+6Bst+4Ct などと書く。 (1) の式は染色体数が,複相 2nの体細胞で 12本,大染色体2本,中2本,小8本であることを意味する。さらに動原体の位置や二次狭窄 (くびれ) を示したのが (2) の式で,m,st,tはそれぞれ中部,次端部,端部にあることを示し,scは二次狭窄の存在を意味している。
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