Nucleic AcidsNucleic Acids

• DNA= • Deoxyribonucleic AcidDeoxyribonucleic Acid• The structure of DNA was not discovered

until 19531953 when WatsonWatson and Crick Crick proposed the structure below.

• DNA is made up of two strands of nucleotidesnucleotides.

• These two strands wind around each other in a double helixdouble helix.

• Each nucleotide is made up of three different parts:

• 1) Phosphate1) Phosphate

• 2) Sugar2) Sugar

• 3) nitrogenous base3) nitrogenous base

• The sugarsugar and phosphatephosphate make chains, and the basesbases 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) AAdenine• 2) GGuanine• 3) CCytosine• 4) TThymine• A purinepurine always pairs with a ppyrimidineyrimidine• AA with TT• CC with GG• Weak hydrogen bondshydrogen bonds hold the nitrogen

bases together.

PurinePurine

pyrimidinepyrimidine

• RNA =• Ribonucleic AcidRibonucleic 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• riboseribose (sugar) instead of deoxyribose deoxyribose• UracilUracil (bases) instead of ThyamineThyamine and• Single strandSingle strand instead of double stranddouble strand

• now Purine pyrimidine

• AdenineAdenine pairs with UracilUracil

• GuanineGuanine pairs with CytosineCytosine

• RNA has three different functions in the cell, depending on its structure. All RNA is single stranded

• Messenger RNA (mRNA) – carries DNA carries DNA code from nucleus to the cytoplasmcode from nucleus to the cytoplasm

• Transfer RNA (tRNA) – brings amino acids brings amino acids to the ribosometo the ribosome

• Ribosomal RNA (rRNA) – puts amino puts amino acids togetheracids together