4.2.2 The Structure of RNA

Structure of RNA:

1. General Structure:

• RNA is a single-stranded polynucleotide chain.
• Contains the sugar ribose, phosphate, and nitrogenous bases (adenine (A), uracil (U), guanine (G), and cytosine (C)).

Types of RNA:

1. Messenger RNA (mRNA):

• Structure:
  • mRNA is a long, single-stranded molecule produced during transcription.
  • Its base sequence is complementary to the DNA template strand.
  • Divided into sequences of three bases called codons, each coding for a specific amino acid.
• Function:
  • Carries the genetic code from DNA in the nucleus to the ribosomes in the cytoplasm, where proteins are synthesised.

2. Transfer RNA (tRNA):

• Structure:
  • tRNA is a small, clover-shaped molecule made by folding into loops due to hydrogen bonding between complementary base pairs.
  • At one end, it has an anticodon, a set of three bases complementary to an mRNA codon.
  • The other end has a binding site for a specific amino acid.
• Function:
  • Transfers the appropriate amino acid to the ribosome during translation.
  • Matches its anticodon with the corresponding mRNA codon, ensuring the correct sequence of amino acids in the protein.

Key Differences Between DNA and RNA:

• RNA is single-stranded; DNA is double-stranded.
• RNA contains uracil (U) instead of thymine (T).
• RNA uses the sugar ribose, while DNA uses deoxyribose.

Key Terms:

• mRNA: Messenger RNA, carries the genetic code from DNA to ribosomes.
• tRNA: Transfer RNA, brings amino acids to ribosomes for protein assembly.
• Codon: A triplet of bases on mRNA.
• Anticodon: A triplet of bases on tRNA that pairs with an mRNA codon.