20 DNA Facts – Fun Facts About DNA

DNA Facts
DNA or deoxyribonuclecic acid is a molecule that encodes genetic information.

DNA or deoxyribonucleic acid is the molecule that codes genetic make-up. Here are 20 interesting and fun facts about DNA:

  1. The genetic code in DNA consists of only four building blocks. These are the nucleotides adenine (A), guanine (G), thymine (T), and cytosine (C).
  2. The DNA molecule forms a double helix. The backbone of the helix consists of phosphates and sugar (deoxyribose), while the nucleotides pair together in the interior of the helix. Adenine always joins with thymine. Guanine always pairs with cytosine.
  3. DNA forms at least three different helix shapes. B-DNA is the helix found in most cells. A-DNA forms a wider right-handed spiral than B-DNA. Z-DNA is a left-handed spiral. While the double helix is the most common shape of DNA, it is not the only one. Single-strand and branched DNA also occur. In 1993, scientists discovered a four-stranded knot called an i-motif or i-DNA.1
  4. The human genome consists of about 3 billion DNA base pairs.
  5. Human DNA is packed into 23 pairs of chromosomes, for a total of 46 chromosomes. The first 22 pairs are called autosomes. The 23rd pair, the sex chromosomes, differ between females (XX) and males (XY).
  6. Friedrich Miescher discovered DNA in 1869. However, it wasn’t known to be genetic information until 1943. Before 1943, most scientists thought proteins stored the genetic code. British molecular biologists James Watson and Francis Crick discovered the structure of DNA on April 25, 1953.
  7. Human beings share 99.9% of their DNA with every other human.2
  8. You share 98.7% of your DNA with chimpanzees and bonobos, the most genetically-similar primates.3
  9. Humans share 60% of genes with fruit flies. Two-thirds of those genes are known to be involved in cancer.4
  10. You also share 85% of your DNA with a mouse and 41% with a banana.5
  11. A human’s closest invertebrate genetic relative is the golden star tunicate. You have more in common, genetically, with this marine animal than you do with an ant, spider, or octopus.
  12. Genes are the part of DNA that code for proteins. Human beings have between 20,000 and 25,000 genes. But, genes only account for about 3% of DNA. Most of a DNA molecule controls the expression of these genes.
  13. Between 5-8% of your DNA isn’t even human. It’s viral DNA, left behind when a virus infected a cell.
  14. A change in DNA is called a mutation. Mutations occur about a thousand times a day, from exposure to ultraviolet light, copying errors (transcription), and other activities. Yet, the cell has so many repair mechanisms that very few mutations last. Some mutations cause disease, such as cancer. Some mutations cause no harm or are beneficial.
  15. Identical twins have the same DNA. However, twins don’t look exactly the same because the environment and lifestyle choices affect gene expression.
  16. The human genome is so long, that if you typed 60 words per minute for eight hours a day it would take you about 50 years to type it out.
  17. DNA is tightly coiled inside a cell, but if you put all the DNA molecules in your body end to end, the DNA would reach from the Earth to the Sun and back over 600 times (100 trillion times six feet divided by 92 million miles).
  18. Almost every living cell in the human body contains DNA. Red blood cells are an exception. These cells lose their nucleus, which contains DNA, as part of their maturation process. Of the vertebrates, only mammalian red blood cells lack DNA. Birds, amphibians, reptiles, and fish all have DNA in their red blood cells.
  19. The largest human gene is called DMD and it codes a protein called dystrophin. The gene consists of 2.3 million bases of 0.08% of the human genome. Dystrophin is a rod-shaped protein found in the cytoplasm of muscle cells.
  20. A person or animal with two completely different DNA profiles is called a chimera. Chimeras are rare, but can occur if a mother retains some fetus DNA, a fetus absorbs a twin, or a person receives a bone marrow transplant.


  1. Gehring, Kalle; Leroy, Jean-Louis; Guéron, Maurice. “A tetrameric DNA structure with protonated cytosine-cytosine base pairs.” Nature. 363: 561–565. doi:10.1038/363561a0
  2. Venter, Craig, Smith, Hamilton O.; Adams, Mark D. (September 1, 2015). “The Sequence of the Human Genome.” Clinical Chemistry 61, 9, 1207–1208. doi:10.1373/clinchem.2014.237016
  3. Prüfer, K., Munch, K., Hellmann, I. et al. (June 13, 2012). “The bonobo genome compared with the chimpanzee and human genomes.” Nature 486, 527–531. doi:10.1038/nature11128
  4. Comparative Genomics Fact Sheet.” (November 3, 2015). National Human Genome Research Institute.
  5. Sanan Media (2013). “The Animated Genome.” Unlocking Life’s Code. Smithsonian Museum of Natural History.