1.5.1 Structure of DNA and RNA

Describe the function of DNA

Holds genetic information which codes for proteins

Describe the function of RNA

Transfers genetic information from DNA to ribosomes

Name the two types of molecules from which a ribosome is made

RNA and proteins

Draw and label a DNA nucleotide

Draw and label an RNA nucleotide

Describe the differences between a DNA nucleotide and an RNA nucleotide

Describe how nucleotides join together to form polynucleotides

Condensation reactions, removing water molecules

Between phosphate group of one nucleotide and deoxyribose / ribose of another

Forming phosphodiester bonds

Describe the structure of DNA

Polymer of nucleotides (polynucleotide)

Each nucleotide formed from

deoxyribose, a phosphate group and a

nitrogen-containing organic base

Phosphodiester bonds join adjacent

nucleotides

2 polynucleotide chains held together by

hydrogen bonds

Between specific complementary base

pairs - adenine / thymine and

cytosine / guanine

Double helix

Describe the structure of (messenger) RNA

Polymer of nucleotides (polynucleotide)

Each nucleotide formed from ribose, a phosphate

group and a nitrogen-containing organic base

Bases - uracil, adenine, cytosine, guanine

Phosphodiester bonds join adjacent nucleotides

Single helix

Compare and contrast the structure of DNA and (messenger) RNA

Suggest how the structure of DNA relates to its functions

Two strands → both can act as templates for semi-conservative replication

Hydrogen bonds between bases are weak → strands can be separated for replication

Complementary base pairing → accurate replication

Many hydrogen bonds between bases → stable / strong molecule

Double helix with sugar phosphate backbone → protects bases / hydrogen bonds

Long molecule → store lots of genetic information (that codes for polypeptides)

Double helix (coiled) → compact

Suggest how you can use incomplete information about the frequency of bases on DNA strands to find the frequency of other bases

% of adenine in strand 1 = % of thymine in strand 2 (and vice versa)

% of guanine in strand 1 = % of cytosine in strand 2 (and vice versa)

Because of complementary base pairing between 2 strands