Lecture on Protein Synthesis

Introduction

• DNA contains genetic information for traits (e.g., eye color).
• Traits are expressed through proteins coded by genes.
• Proteins are crucial for functions such as transport, structure, enzyme activity, and protection.

Protein Synthesis

• The process by which DNA leads to protein creation.
• Two main steps: Transcription and Translation.

Transcription

• Occurs in the nucleus.
• Involves RNA polymerase connecting complementary RNA bases to DNA, forming mRNA (messenger RNA).
• mRNA is a single-stranded message based on DNA.
• mRNA undergoes editing before being functional.
• Once ready, mRNA exits the nucleus and enters the cytoplasm.

Translation

• Occurs in the cytoplasm at the ribosome (made of rRNA).
• Involves tRNA (transfer RNA) which carries amino acids, the building blocks of proteins.
• mRNA directs which tRNAs come with specific amino acids.
• tRNA reads mRNA codons (triplets of bases) and brings complementary amino acids.
• Process:
  • Codon: A sequence of three mRNA bases (e.g., AUG).
  • Anticodon: A complementary tRNA sequence (e.g., UAC).
  • Amino acids are added in sequence as tRNA matches codons on mRNA.
• Use of a codon chart helps determine which amino acid each codon corresponds to.

Examples

• Start codon (AUG) codes for methionine, the initial amino acid.
• Multiple codons can code for the same amino acid (e.g., various codons for leucine).

Protein Assembly

• Amino acids are linked by peptide bonds, forming a polypeptide chain.
• The process continues until a stop codon is reached.
• The chain then undergoes folding and modification.

Conclusion

• DNA directs protein synthesis with the help of mRNA, rRNA, and tRNA.
• Proteins are essential for life and have diverse roles.
• Further exploration: Protein folding and transport.

Stay curious to learn more about these biological processes!