Strandedness of chromosomes.

TLDR: Considerable amount of experimental evidence has provided results consistent with the observational appearance of half-chromatids, and the effects of incorporated isotopes are expressed in generations succeeding labeling.

Abstract: Publisher Summary Various observational evidences indicate that chromosomes are multistranded. These observations are obtained by light microscopic studies on organisms containing large chromosomes. The two half-chromatids separate quite far from one another and can be found interwound over great distances along their length. In favorable material the separation can be found even in prophase and metaphase. Considerable amount of experimental evidence has provided results consistent with the observational appearance of half-chromatids. The evidence falls into five different categories dealing with (1) the types of aberrations induced in late prophase or metaphase by radiation, (2) the types of aberrations induced by radiation at the end of G 1 before the chromosomes have replicated, (3) experiments in which chromosome structure has been unraveled by treatment with enzymes or other agents, (4) the distribution of labeled DNA among the chromosomes at mitoses subsequent to labeling, and (5) experiments in which the effects of incorporated isotopes are expressed in generations succeeding labeling.