Nearly all cells in the human body contain 46 chromosomes in 23 pairs, with 1 chromosome 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 functioning of the organism. The totality of an individual"s genes is the genotype, and the person"s actual characteristics 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.