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 (mRNA) – carries DNA
code from nucleus to the cytoplasm
• Transfer RNA (tRNA) – brings amino acids
to the ribosome
• Ribosomal RNA (rRNA) – puts amino
acids together