A threadlike, deeply stained, structure contained in the nucleus of a cell of eukaryotic organisms and composed mainly of DNA and protein in the form of chromatin. Each chromosome consists of two chromatids bound together at the centromere. According to classical genetics, it is the bearer of the genes in a linear order and thus like ‘beads on a string’, which molecular genetics now compares to ‘a string on the beads’. As for all diploid organisms, human cells normally have 46 chromosomes or 23 pairs (22 matched pairs and one pair of sex chromosomes), with one of each pair being contributed by the mother and the other by the father at conception. The number of chromosomes is constant for the somatic cells into which chromatin resolves itself during mitosis and meiosis. The anatomist Heinrich Wilhelm Gottfried Waldeyer-Hartz (1836-1921) introduced the term ‘chromosome’ in 1888. Following August Weismann (1834-1914), it was previously referred to as the idant. It was Joe Hin Tjio, in 1955, who defined 46 as the exact number of human chromosomes. Did you know that gorillas and potatoes have two more chromosomes that humans?
See Allele, Anaphase, Autism, Behavioral phenotype syndrome, Caenorhabditis (C.) elegans (or nematode), Centromere, Chromatid, Chromatin, Conditional knockouts, Copying errors, Cytoplasm, Diploid, DNA (deoxyribonucleic acid), Downs’ syndrome, Edwards syndrome, Eukaryote cell (or organism), Fibroblast growth factor, Fragile X syndrome, Gene, Genetic (or DNA) recombination, Gemone, Germ plasm, Haploid, Histone, Karyotyping, Limkinase 1 gene, Lissencephaly, Meiosis (or reduction division), Metaphase, Microtubules, Mitosis, Mosaicism, Mutation (biology), Non-dysjunction, Nucleus (of a cell), Proteins, Spindle, Polygenes, Praderr-Willi syndrome, Protoplasm, Theory of the germ plasm, Trisomy 21