Nucleic Acids DNA Deoxyribonucleic Acid The structure of

Nucleic Acids

• • • DNA= Deoxyribonucleic Acid The structure of DNA was not discovered until 1953 when Watson and Crick proposed the structure below. • DNA is made up of two strands of nucleotides • These two strands wind around each other in a double helix

• Each nucleotide is made up of three different parts: • 1) Phosphate • 2) Sugar • 3) nitrogenous base • The sugar and phosphate make chains, and the bases connect the two strands of DNA together.

• Draw the structure of DNA below and circle the nucleotides.

• There are 4 different nitrogen bases called: • 1) Adenine Purine • 2) Guanine • 3) Cytosine pyrimidine • 4) Thyamine • A purine always pairs with a pyrimidine • A with T • C with G • Weak hydrogen bonds hold the nitrogen bases together.

• RNA = • Ribonucleic Acid • RNA is very similar to DNA. RNA nucleotides are also made up of three parts: sugar, phosphate, and one of four nitrogen bases. • RNA DNA • ribose (sugar) instead of deoxyribose • Uracil (bases) instead of Thyamine and • Single strand instead of double strand

• now Purine pyrimidine • Adenine pairs with Uracil • Guanine pairs with Cytosine • RNA has three different functions in the cell, depending on its structure. All RNA is single stranded

• Messenger RNA (m. RNA) – carries DNA code from nucleus to the cytoplasm • Transfer RNA (t. RNA) – brings amino acids to the ribosome • Ribosomal RNA (r. RNA) – puts amino acids together