<P> In humans, eye color is an example of an inherited characteristic: an individual might inherit the "brown - eye trait" from one of the parents . Inherited traits are controlled by genes and the complete set of genes within an organism's genome is called its genotype . </P> <P> The complete set of observable traits of the structure and behavior of an organism is called its phenotype . These traits arise from the interaction of its genotype with the environment . As a result, many aspects of an organism's phenotype are not inherited . For example, suntanned skin comes from the interaction between a person's phenotype and sunlight; thus, suntans are not passed on to people's children . However, some people tan more easily than others, due to differences in their genotype: a striking example is people with the inherited trait of albinism, who do not tan at all and are very sensitive to sunburn . </P> <P> Heritable traits are known to be passed from one generation to the next via DNA, a molecule that encodes genetic information . DNA is a long polymer that incorporates four types of bases, which are interchangeable . The sequence of bases along a particular DNA molecule specifies the genetic information: this is comparable to a sequence of letters spelling out a passage of text . Before a cell divides through mitosis, the DNA is copied, so that each of the resulting two cells will inherit the DNA sequence . A portion of a DNA molecule that specifies a single functional unit is called a gene; different genes have different sequences of bases . Within cells, the long strands of DNA form condensed structures called chromosomes . Organisms inherit genetic material from their parents in the form of homologous chromosomes, containing a unique combination of DNA sequences that code for genes . The specific location of a DNA sequence within a chromosome is known as a locus . If the DNA sequence at a particular locus varies between individuals, the different forms of this sequence are called alleles . DNA sequences can change through mutations, producing new alleles . If a mutation occurs within a gene, the new allele may affect the trait that the gene controls, altering the phenotype of the organism . </P> <P> However, while this simple correspondence between an allele and a trait works in some cases, most traits are more complex and are controlled by multiple interacting genes within and among organisms . Developmental biologists suggest that complex interactions in genetic networks and communication among cells can lead to heritable variations that may underlie some of the mechanics in developmental plasticity and canalization . </P>

What part of the cell is heredity information found