If you could unwind the DNA from just one of your cells and lay it end to end, it would stretch about two metres. It is folded into a nucleus a few thousandths of a millimetre wide. You have tens of trillions of cells, and nearly all of them carry the full set.
That DNA spells out instructions in just four chemical letters, A, C, G and T, in a sequence about three billion letters long. Reading it out at one letter a second, day and night, would take you about 95 years. Your body copies it, with astonishing accuracy, millions of times every second.
“We will show them Our signs on the horizons and within themselves, until it becomes clear to them that it is the truth.”
Qur'an 41:53 · our rendering
This verse near the end of Surah Fussilat promises signs in two directions: outward, in the world and the sky ('the horizons'), and inward, in the human self. Muslim writers have found in it a lifelong invitation to study both. We place it here because DNA is one of the most intimate 'signs within themselves' there is.
What science shows
DNA (deoxyribonucleic acid) is a long molecule shaped like a twisted ladder, the famous double helix. The 'rungs' are pairs of chemical bases: A always pairs with T, and C always pairs with G. Because each side of the ladder mirrors the other, a cell can unzip the molecule and use each half as a template to build a new partner. That is how life copies its instructions.
The structure was worked out in 1953 by James Watson and Francis Crick in Cambridge, using X-ray images made at King's College London by Rosalind Franklin and her student Raymond Gosling, especially 'Photo 51'. Franklin's crucial contribution was long under-recognised; she died in 1958, and the 1962 Nobel Prize went to Watson, Crick and Maurice Wilkins. Today she is widely honoured as a co-discoverer in all but name.
Long before anyone knew what DNA was, an Augustinian friar in Brno, Gregor Mendel, worked out the basic rules of inheritance by growing and crossing about 28,000 pea plants between 1856 and 1863. He showed that traits pass on in units we now call genes. His work was ignored for 34 years, then rediscovered in 1900.
The Human Genome Project, an international effort involving the Wellcome Sanger Institute near Cambridge, published an essentially complete human sequence in 2003; the last gaps were filled in 2022. It found that humans have only about 20,000 protein-coding genes, fewer than many expected, and that only a small fraction of our DNA codes for proteins at all. The rest helps switch genes on and off, shapes chromosomes, or still puzzles scientists.
Copying three billion letters every time a cell divides is risky, so cells have proofreading and repair systems. After proofreading, DNA copying makes roughly one mistake in every billion letters. The 2015 Nobel Prize in Chemistry went to Tomas Lindahl, Paul Modrich and Aziz Sancar for showing how cells repair damaged DNA. Sancar, born in Turkey, has spoken of his Muslim upbringing and his gratitude to his family.
Perhaps the most striking finding is how alike we are. Any two people share about 99.9 per cent of their DNA. The genetic differences between people within any one population are larger than the average differences between populations. In the language of the genome, humanity is one family, and every member of it is still unique.
What each faith says
Judaism
“For Thou hast made my reins; Thou hast knit me together in my mother's womb. I will give thanks unto Thee, for I am fearfully and wonderfully made; Wonderful are Thy works; and that my soul knoweth right well. My frame was not hidden from Thee, When I was made in secret, And curiously wrought in the lowest parts of the earth. Thine eyes did see mine unformed substance, And in Thy book they were all written— Even the days that were fashioned, When as yet there was none of them.”
Psalm 139:13-16 · JPS 1917
Psalm 139 is a song about being known completely by God, even before birth: 'Thine eyes did see mine unformed substance, and in Thy book they were all written.' Many Jewish readers today hear a new echo in its picture of a life 'written' and 'knit together' in secret.
The Mishnah (Sanhedrin 4:5) teaches why God began humanity with one person: so that no one could say 'my ancestor is greater than yours', and to show God's greatness. 'A person stamps many coins with one seal and they are all alike; but the King of kings stamped every human being with the seal of the first human, and not one of them is like another' (our rendering). It is a remarkable description of a shared inheritance that still makes everyone unique.
Christianity
“I will give thanks to you, for I am fearfully and wonderfully made. Your works are wonderful. My soul knows that very well.”
Psalm 139:14 · WEB
Francis Collins, who led the Human Genome Project in the United States, is a committed Christian. On the day the first draft was announced in 2000, he said it gave a first glimpse of 'our own instruction book, previously known only to God'. He later wrote The Language of God (2006) and founded BioLogos, which promotes conversation between evangelical faith and evolutionary science.
Christians teach that every person is made in the image of God (Genesis 1:27), whatever their genes. Mendel, the founder of genetics, lived and died a friar and became abbot of his monastery. Christians today hold different views on how evolution and Genesis fit together, but nearly all agree that human dignity rests on God, not on DNA.
Islam
“O people, We created you from a male and a female and made you into nations and tribes so that you may come to know one another.”
Qur'an 49:13 · our rendering
The Qur'an describes human creation in stages and invites wonder at it: 'O human being, what has deceived you about your generous Lord, who created you, shaped you and proportioned you, assembling you in whatever form He willed?' (82:6-8). God is al-Musawwir, the Fashioner, who gives each thing its form.
The Qur'an also speaks of human unity and diversity together: 'O people, We created you from a male and a female and made you into nations and tribes so that you may come to know one another. The most honoured of you in the sight of God is the most mindful of Him' (49:13). Many Muslims find that the 99.9 per cent we share, and the small differences that make each person unique, fit this verse closely, not as a scientific claim but as a moral one.
Same and different
All three faiths teach that humanity has a common origin and that every person has equal dignity, and all three find the genome a moving picture of that. They hold a range of views on evolution, within and between traditions. They differ in how they ground human worth: in the image of God (Judaism and Christianity), or in God's honouring of the children of Adam (peace be upon him) (Qur'an 17:70) without speaking of an 'image'.
A moment to reflect
- You share 99.9 per cent of your DNA with every other person. Why do the 0.1 per cent differences seem to matter so much to us?
- Is it fair that Rosalind Franklin was not credited at the time? How should we honour people whose work goes unseen?
- Does knowing your genes tell you who you are? What else does?
- The Mishnah says every person is stamped from one seal yet unique. How would you explain that to a child?
Watch
Award-winning molecular animation of DNA at work inside the cell, from Drew Berry at WEHI.
Wellcome's yourgenome shows how DNA is read to make a protein, in under three minutes.
How a cell copies its DNA, in 3D.
TED-Ed on Rosalind Franklin and Photo 51.
Do it together
Mash a strawberry in a bag with washing-up liquid, salt and water, filter it, and gently pour cold rubbing alcohol on top (with adult supervision). Pale strands of DNA rise into view.
Draw a giant family tree on a wall where everyone adds their family's countries of origin. Then read Qur'an 49:13 and Mishnah Sanhedrin 4:5 and talk about one humanity with many branches.
Visit the Science Museum in London, or walk past the Eagle pub and the Cavendish in Cambridge, where the double helix was announced. Talk about how discoveries depend on teams, not just famous names.
Go deeper
- What is DNA? (yourgenome, Wellcome Connecting Science) · article
- Human Genome Project fact sheet (NHGRI) · article
- Franklin and Gosling, Molecular configuration in sodium thymonucleate (Nature, 1953) · paper
- Psalm 139 (Sefaria) · scripture
- Surah al-Hujurat 49:13 (Quran.com) · scripture
Sources (9)
- About 2 m of DNA in each cell; genome about 3 billion base pairs: NHGRI, Deoxyribonucleic acid fact sheet
- Watson and Crick structure (1953) using Franklin and Gosling's Photo 51: Franklin and Gosling, Nature 171, 740 (1953)
- Nobel Prize 1962 to Watson, Crick and Wilkins: Nobel Prize in Physiology or Medicine 1962
- Mendel's pea experiments (1856-1863), rediscovered 1900: Britannica, Gregor Mendel
- Human Genome Project completed 2003; about 20,000 protein-coding genes: NHGRI, Human Genome Project
- First complete, gapless human genome (2022): Nurk et al., Science 376, 44 (2022)
- Nobel Prize in Chemistry 2015 for DNA repair (Lindahl, Modrich, Sancar): Nobel Prize, 2015
- Humans share about 99.9% of their DNA; most variation is within populations: NHGRI, Genetics vs genomics / human variation
- Collins's 'instruction book' remark at the June 2000 announcement: NHGRI, June 2000 White House remarks
