SG

DNA and Protein Synthesis Review Notes

DNA and Protein Synthesis

  • Monomer unit of nucleic acids: Nucleotides

  • Nucleotide Structure:

    • A nucleotide consists of three parts: a phosphate group, a pentose sugar (deoxyribose in DNA or ribose in RNA), and a nitrogenous base.

  • Four Bases of DNA:

    • Adenine (A), Guanine (G), Cytosine (C), and Thymine (T)

  • Base Pairing Rules of DNA:

    • Adenine (A) pairs with Thymine (T)
    • Guanine (G) pairs with Cytosine (C)
    • This pairing is due to hydrogen bonds between the bases.

  • Shape of DNA:

    • Double helix: two strands of DNA wind around each other.

  • Complementary DNA Strand:

    • Given strand: A C C T A C G G A T C G A C T
    • Complementary strand: T G G A T G C C T A G C T G A

  • DNA Replication:

    • DNA replication is the process by which a DNA molecule is duplicated.
    • It is a semi-conservative process (each new DNA molecule consists of one original strand and one new strand).

  • Enzymes in DNA Replication:

    • Helicase: Unwinds the DNA double helix.
    • DNA Polymerase: Adds nucleotides to the growing DNA strand, following base pairing rules. It also proofreads the new strand.
    • Ligase: Joins DNA fragments (Okazaki fragments on the lagging strand).
    • Primase: Synthesizes RNA primers to initiate DNA synthesis.

  • Compare and Contrast DNA and RNA

    • DNA (Deoxyribonucleic Acid):
      • Sugar: Deoxyribose
      • Bases: Adenine, Guanine, Cytosine, Thymine
      • Structure: Double-stranded helix
      • Location: Primarily in the nucleus
      • Function: Stores genetic information
    • RNA (Ribonucleic Acid):
      • Sugar: Ribose
      • Bases: Adenine, Guanine, Cytosine, Uracil
      • Structure: Single-stranded
      • Location: Nucleus and cytoplasm
      • Function: Involved in protein synthesis

  • Transcription (DNA to mRNA):

    • Given DNA strand: TAC GGG CAT TAA ACC
    • mRNA sequence: AUG CCC GUA AUU UGG

  • Amino Acids from mRNA Sequence:

    • Given mRNA sequence: AUG CCC GUA AUU UGG
    • Amino acid sequence: Methionine - Proline - Valine - Isoleucine - Tryptophan

  • Three Types of RNA:

    • mRNA (messenger RNA): Carries genetic information from DNA in the nucleus to the ribosome in the cytoplasm.
    • tRNA (transfer RNA): Carries amino acids to the ribosome during translation.
    • rRNA (ribosomal RNA): A component of ribosomes.

  • Gene:

    • A segment of DNA that contains the instructions for making a specific protein or functional RNA molecule.
      • Function: Determines traits by coding the sequence of amino acids for proteins.

  • Transcription Process (Beginning to End):

    1. Initiation: RNA polymerase binds to the promoter region of the DNA.
    2. Elongation: RNA polymerase moves along the DNA template, synthesizing mRNA by adding nucleotides complementary to the DNA strand (A with U, G with C).
    3. Termination: RNA polymerase reaches a termination signal, and the mRNA molecule is released.
    • Enzyme: RNA polymerase

  • Translation Process (Beginning to End):

    1. Initiation: Ribosome binds to mRNA at the start codon (AUG).
    2. Elongation: tRNA molecules, each carrying a specific amino acid, bind to the mRNA codons in the ribosome. The amino acids are joined together by peptide bonds to form a polypeptide chain.
    3. Termination: The ribosome reaches a stop codon on the mRNA, and the polypeptide chain is released.

  • Terms:

    • Transcription: The process of copying a segment of DNA into RNA.
    • Translation: The process of synthesizing a protein from mRNA.
    • DNA: Deoxyribonucleic acid, the genetic material of the cell.
    • mRNA: Messenger RNA, carries genetic code from DNA to ribosomes.
    • Ribosome: Site of protein synthesis.
    • tRNA: Transfer RNA, brings amino acids to the ribosome.
    • Amino Acid: Monomer of a protein.
    • Polypeptide: A chain of amino acids linked by peptide bonds.
    • Nucleus: The organelle containing the cell's DNA.
    • Codon: A sequence of three nucleotides in mRNA that codes for a specific amino acid or stop signal.
    • Anticodon: A sequence of three nucleotides in tRNA that is complementary to a codon in mRNA.

  • Number of Amino Acids and Codons:

    • There are 20 amino acids.
    • There are 64 codons (61 code for amino acids, and 3 are stop codons).