DNA TRANSCRIPTION

DNA and its Function

  • DNA as a Molecular Blueprint

    • DNA carries a vast amount of genetic information.

    • Functions as a blueprint for producing cellular components but cannot execute actions on its own.

    • Proteins act as the "molecular workers" that manage cellular tasks.

The Flow of Information

  • Role of RNA

    • DNA is housed in the nucleus of cells.

    • Protein synthesis occurs in ribosomes.

    • RNA serves as the intermediary for transferring information from DNA to ribosomes for protein synthesis.

RNA Structure

  • Differences from DNA

    • RNA is a single-stranded molecule.

    • Contains the sugar ribose instead of deoxyribose.

    • Uses uracil in place of thymine.

Types of RNA

  • RNA Types Encoded by DNA

    • Messenger RNA (mRNA):

      • Transports the genetic code for amino acids from DNA to ribosomes.

      • Contains codons that specify the sequence of amino acids in proteins.

    • Ribosomal RNA (rRNA):

      • Major component of ribosomes and is crucial for protein synthesis.

    • Transfer RNA (tRNA):

      • Delivers specific amino acids to the ribosome for protein assembly.

    • Viral RNA:

      • Associated with viruses like HIV.

    • Enzymatic RNA:

      • RNA that catalyzes biochemical reactions.

    • MicroRNA:

      • Regulates gene expression and plays a role in disease prevention.

Messenger RNA (mRNA)

  • Function:

    • mRNA carries coded information for proteins from DNA in the nucleus to the ribosomes.

    • Ribosomes utilize this information to synthesize proteins based on the mRNA's base sequence.

    • Codons:

      • Groups of three nucleotides on mRNA that correspond to specific amino acids in a protein.

Ribosomal RNA (rRNA)

  • Ribosome Structure:

    • Composed of rRNA and numerous proteins.

    • Subunits:

      • Consists of a small subunit and a large subunit, each with specific sites for mRNA and tRNA.

    • Function:

      • Catalyzes the translation process, joining the mRNA and tRNA.

Transfer RNA (tRNA)

  • Delivery of Amino Acids:

    • tRNA transports specific amino acids to ribosomes during protein synthesis.

    • Cells produce at least one type of tRNA for each amino acid.

    • Charging process:

      • Enzymes in the cytoplasm attach the appropriate amino acid to tRNA using ATP energy.

Amino Acids

  • Constituents of Proteins:

    • Organic compounds that link together to form proteins.

    • Classification:

      • Essential Amino Acids: Must be obtained through diet (e.g., histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine).

      • Non-Essential Amino Acids: Can be synthesized by the body (e.g., alanine, asparagine, aspartic acid, glutamic acid).

      • Conditional Amino Acids: Usually non-essential but can become essential under stress or illness (e.g., arginine, cysteine, glutamine, tyrosine, glycine, ornithine, proline, serine).

Further Learning

  • Tasks & Questions:

    • Investigate the structure and functions of ribosomes in eukaryotic cells.

    • Identify five sources of essential amino acids and the specific amino acids they contain.