new human being are coded into the DNA molecule. It is shaped like a ladder twisted into a spiral. The two long upright strands are joined by a series of rungs of pairs of amino acids, which can only join together in a limited number of ways. The pattern in which these pairs appear is the code built into the DNA molecule, and groups of these connections form genes. Each DNA molecule is built up of between 100,000 to 10 million atoms. There are 46 chromosomes in the full human set: 23 came from the mother and were in the egg cell, and 23 came from the father in the sperm cell. Every time a cell devides, each piece of DNA in every chromosome is copied.