Nearly all cells in the human body contain 46 chromosomes in 23 pairs, with 1 chromo- some in each pair inherited from the mother and the other inherited from the father. Chromosome: sausage-shaped structure in the nucleus of cells, containing genes, which are paired, except in reproductive cells. Dna: long strand of cell material that stores and transfers genetic information in all life forms. Dna in chromosomes are organized into segments called genes. Genes: segment of dna containing coded instructions for the growth and func- tioning of the organism. The totality of an individual"s genes is the genotype, and the person"s actual character- istics are called the phenotype. Phenotype: organism"s actual characteristics derived from its genotype. Dominant-recessive inheritance is another aspect of genetic functioning that influences the relation between genotype and phenotype. Dominant-recessive inheritance: pattern of inheritance in which a pair of chromosomes contains one dominant and one recessive gene, but only the dominant gene is expressed in the phenotype.