DNA is the code for all of life. Francis Crick and James Watson, two molecular biologists, proposed the model of the double helix of polysaccharides (deoxyribose) that are interconnected by four types of nucleic acids that are always (almost always) in the same pairs: Adenine -Thymine, and Guanine-Cytosine. For 
that, they received the Nobel Prize in 1962. Chromosomes contain most of the DNA which is transmitted to the offspring, half by the mother and half by the father. There is DNA outside of the chromosomes in the mitochondria, the “powerhouse” of the cell. This DNA comes entirely from the mother.
Crick’s pencil drawing of their concept of what DNA looks like
The patterned sequence in which these base pairs appear on the ladder of the spiral determines the code which directs the cells to make everything from whether you become a worm or a rocket scientist. A segment of code pertaining to a single characteristic is called a gene. There are over three-billion base pairs spread over 23 chromosome pairs. A number of base pairs constitute one gene. It is estimated that the number of genes for humans is around 20,000.
Mapping our entire genetic makeup, the human genome, has become the gold standard in the study of a whole slew of science subdivisions. In criminology, we can determine who the killer is from just a small sample of his or her body cells. Paternity can be established without a doubt. Clever ways of collecting specimens have included getting samples of saliva off stamps. The suspect was trapped by sending back a letter to collect supposed lottery winnings. The various genealogy organizations that promise to help you find your ancestry are a veritable treasure trove for DNA evidence, and have already yielded a number of notorious convictions.
In paleontology, we can determine who is related to whom and by what routes they populated the earth. As yet, health insurance companies have not to date used genetic data to weed out those people that have a genetic predisposition for various diseases, but my guess is that it is just around the corner.
Genes can now be spliced, removing a harmful segment and replacing it with a beneficial code. This can also be used to treat genetic diseases, but could be misused to change the fetus’s traits, designer babies with blue eyes and blond hair, smarter, better athletes, or even more sinister characteristics are now possible! Wait until the Olympic Committee has to deal with GMA’s (genetically modified athletes).
Cancer is a disease of the cell’s DNA that directs the cell to multiply without a purpose that then invades and pushes out the healthy cells. We are beginning to attack this dreaded disease by altering the DNA to make it behave, or make it more susceptible to our chemotherapy.
GMO (Genetically Modified Organisms) has a bad reputation. People read package labeling and avoid anything that smacks of genetic alteration. But contrary to popular opinion, just such manipulation has saved billions from starvation. Norman Borlaug, an agronomist, crossbred wheat to increase the yield by at least 300% through making it more resistant to disease, creating a strain with a double wheat season, and making a shorter (dwarf) plant that is not damaged by heavy storms. It is practically impossible to get non-GMO bread anymore. Norman Borlaug received the Nobel Peace Prize in 1970 because he improved the world food supply, saving many lives. As Thomas Malthus, the economist, warned, the lack of food leads to wars.
97% of scientists believe that humans developed from earlier species of animals. In the US, 40% believe that is the case, while 40% do not, and 20% are not sure. The only country that has a higher percentage of “creationists” is Turkey, where 50% do not believe we evolved.
Men are forced to pay child support, and people are sentenced to life imprisonment, while others have been exonerated based on genetic tests. DNA is accepted as a valid and proven means of certain identification. The odds that two people (not twins) have the same DNA is 1 in 70,000,000,000,000 (70 trillion). Putting this in perspective, winning Powerball odds are roughly 1 in 300,000,000. Finding a genetically identical human would be 233,333 times less likely than winning at Powerball, or put another way it would take nearly 8,750 times our current world population of 8 billion to make it mathematically possible to find two (non-twin) identical human beings on earth, not impossible just very, very unlikely.
98.5% of the gene sequence of the chimpanzee is identical to ours, while we only share 44% of the genes of Drosophila melanogaster, the fruit fly. I am just guessing, but I will bet we are more closely related to chimpanzees than fruit flies. DNA does not lie!
We have sequenced the genome of Australopithecus, Denisovans, Neanderthals, and other hominids. Lo and behold, we have even more DNA in common with them. Some of our population has a higher percentage of these early human genes than others. You can occasionally see them in the throng of people at the mall, and even have to deal with them on a one on one basis. They are easily identifiable not only by appearance, but also by their tell-tale neolithic intellect. It appears that there was a lot of crossbreeding going on in the last 100,000 years. It is likely that much of it was consensual, but undoubtedly not all of it. I suspect that paternity suits were not all that common then, and the “me too movement” was not yet well established.