<P> DNA usually occurs as linear chromosomes in eukaryotes , and circular chromosomes in prokaryotes . The set of chromosomes in a cell makes up its genome ; the human genome has approximately 3 billion base pairs of DNA arranged into 46 chromosomes . The information carried by DNA is held in the sequence of pieces of DNA called genes . Transmission of genetic information in genes is achieved via complementary base pairing . For example , in transcription , when a cell uses the information in a gene , the DNA sequence is copied into a complementary RNA sequence through the attraction between the DNA and the correct RNA nucleotides . Usually , this RNA copy is then used to make a matching protein sequence in a process called translation , which depends on the same interaction between RNA nucleotides . In alternative fashion , a cell may simply copy its genetic information in a process called DNA replication . The details of these functions are covered in other articles ; here the focus is on the interactions between DNA and other molecules that mediate the function of the genome . </P>
where can you find dna in the body
chromosomes in a cell