Who Discovered DNA?

Erwin Chargaff. 1950

• At the time scientists knew that DNA was made of nucleotides but did not know what DNA looked like.

• Chargaff found that the number of Adenine and Guanine was equal to the number of Thymine and Cytosine.

Who Discovered DNA?

Maurice Wilkins and Rosalind Franklin

• Franklin used X-rays to try and see the structure of DNA.

• Franklin was the first to discover the basic dimensions of DNA.

• Wilkins took some of his and Franklin's data and showed it to James Watson and Francis Crick.

​Maurice Wilkins

​Rosalind Franklin

Who Discovered DNA?

James Watson and Francis Crick

• Watson and Crick used X-Ray data from Wilkins and Franklin and built the first accurate model of DNA.

• In 1953, they published their findings in the journal Nature.

• Watson, Crick, and Wilkins received a Nobel Prize for their findings. Franklin did not. Even if they had acknowledged what she had done she could not share the Nobel Prize because she passed away.

James Watson

Francis Crick

What is DNA?

• DNA stands for deoxyribonucleic acid

• DNA determines organism's traits.

• The sections of DNA that influence each trait are called genes.

How is DNA Structured?

• The shape of DNA is called a double helix.

• Made up of two main parts

  • One of the parts is the sugar-phosphate backbone. This forms the sides of the DNA molecule.

  • The other part is nitrogen bases. This is where the genetic code is stored.

    • The nitrogen bases are Adenine, Guanine, Cytosine, and Thymine.

Base Pairing

• Nitrogen bases only pair one way

  • Adenine to Thymine

  • Cytosine to Guanine

• Nitrogen bases are held together by hydrogen bonds.

• A set of the nitrogen base, sugar, and phosphate is called a nucleotide.