structural carrier of hereditary characteristics, found in the cell nucleus. The number of chromosomes is characteristic of each species; in sexually reproducing species, chromosomes generally occur in pairs. In MITOSIS, or ordinary cell division, each individual chromosome is duplicated and each daughter cell receives all chromosomes, a set exactly like its parent's. In MEIOSIS, the process by which sex cells (OVUM and SPERM) are formed, each daughter cell receives half the number of chromosomes, one of each pair. A fertilized egg contains two sets of chromosomes, one set from each parent. Chromosomes are made of protein and NUCLEIC ACID. They represent the linear arrangement of GENES, the units of inheritance.