History of DNA

what did Mendel discover?

• 1866

• established the principles of inheritance - dominance, segregation and independent assortment

what did Miescher discover?

• 1869

• first isolated DNA

• called it nuclein

what did Flemming discover?

• 1882

• described chromosome separation during mitosis

how did Griffith establish DNA as genetic material?

• 1928

• demonstrated bacterial transformation

how did Avery, MacLeod and McCarthy establish DNA as genetic material?

• 1944

• identified DNA as the transforming material

how did Hershey and Chase establish DNA as genetic material?

• 1952

• showed that viral DNA, rather than protein, enters bacterial during infection

what are Chargaff’s rules?

• Adenine (A) = Thymine (T)

• Guanine (G) = Cytosine (C)

these relationships helped establish complementary DNA base pairing

how was the DNA double-helix structure discovered?

• Franklin and Gosling (1952) = produced X-ray diffraction images of DNA

• Watson and Crick (1953) = used X-ray evidence and Chargaff’s rules to propose the double-helix model

what did the Human Genome Project establish?

• 2003 = produced the first essentially complete human genome sequence

• the human genome contains approx 3 billion base pairs and around 20,000 genes

• 2022 = remaining sequence gaps were filled