Chromosomes are dark-staining, threadlike structures in the cell nucleus composed of DNA and chromatin that carry genetic information (definition after Nussbaum et al and Mueller and Young).Formalized standard nomenclature for human chromosomes dates from 1960 and, since 1978, has been known as the International System for Human Cytogenetic Nomenclature (ISCN).Material in this section is based on recommendations in ISCN 2005. Earlier reports have also been consulted.Human chromosomes are numbered from largest to smallest from 1 to 22. There are 2 additional chromosomes, X and Y. The numbered chromosomes are known as autosomes, X and Y as the sex chromosomes. Chromosomes ...
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