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One set is inherited from the father, and one set is inherited from the mother. A DNA is a sort of a bio molecule. The entire DNA in cells can be found in individual pieces that are called chromosomes. The main difference between DNA and chromosome is regarding the role of genes. DNA stands for deoxyribonucleic acid. The DNA is basically made up of cytosine, adenine, thymine and guanine. When you arrange these four bases to create a particular segment, it is called a gene.
What is a gene? A gene is the basic physical and functional unit of heredity. Genes, which are made up of DNA, act as instructions to make molecules called proteins. In humans, genes vary in size from a few hundred DNA bases to more than 2 million bases. The Human Genome Project has estimated that humans have between 20,000 and 25,000 genes. Every person has two copies of each gene, one inherited from each parent. Most genes are the same in all people, but a small number of genes (less than 1 percent of the total) are slightly different between people. Alleles are forms of the same gene with small differences in their sequence of DNA bases.