Unravelling the code of life

1869: Nuclein – now known as DNA or deoxyribonucleic acid – isolated from nuclei of white blood cells

1879: Chromosomes discovered within nucleus of cell

Nucleus

1900: Building blocks of DNA established as phosphate and sugar (deoxyribose) and four bases (nucleotides) adenine (A), cytosine (C), guanine (G), thymine (T)

1933: Chromosomes shown to contain DNA

1941: “One gene- one protein” hypothesis

1944: Discovery that DNA, not protein, is material of inheritance

1953: James Watson and Francis Crick (clockwise from top left) – guided by X-ray photographs taken by Maurice Wilkins and Rosalind Franklin – discover double-helix structure of DNA

1961: Marshall Nirenberg deciphers genetic code, revealing sequence of amino acids in protein molecules

1977: Walter Gilbert and Frederick Sanger devise techniques for sequencing order of base pairs

1986: Leroy Hood develops first high-speed automated DNA sequencer

1990: Human Genome Project begins with goal of sequencing nucleotides and mapping all genes in human DNA

June 2000: U.S. President Bill Clinton announces that 85% of genome has been sequenced. Research now shifts to discovering how individual genes within chromosomes vary

2006: Sequence of last human chromosome published. Chromosome 1 is largest with 4,316 genes, made up of some 249 million base pairs

1 Human cell: Nucleus of every cell contains 46 chromosomes, 23 from each parent

2 Chromosome: Each chromosome is comprised of one tightly coiled molecule of DNA with proteins that serve to package DNA and control its functions. DNA carries unique genetic code that determines characteristics of each person

DNA: Uncoiled molecule is so large that average chromosome contains 50mm of DNA

3 Genome: DNA is made of chemical bases A, C, G and T. Each A base bonds with T base and each G base with C

4 Genetic code: Order of nucleotides within gene is inheritable instructions needed to make protein molecules

Some proteins are building materials of cells – skin, heart, blood – while
others control biological processes such as digesting food or carrying oxygen in blood 

5 Mutations: Alterations to sequence of code can result in proteins with incorrect form and shape. Scientists have identified more than 6,000 gene disorders which affect about one in 200 people

6 Personal genomes: New-generation sequencing techniques may eventually identify risks of
genetic diseases and suggest therapies

Cost per human genome (2001)  $95.3 million


Cost per genome (2017) $1,121

Gene 
Protein


Sources: The Double Helix by James Watson, Nature, Life Technologies
Pictures: Associated Press, National Library of Medicine
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