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General Biology: Translation and Genetic Code

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  • What is the central dogma of molecular biology?

    The central dogma describes the flow of genetic information: DNA is transcribed into RNA, which is then translated into protein.

  • What direction is mRNA read during translation?

    mRNA is read by the ribosome in the 5’ to 3’ direction during translation.

  • What is a codon?

    A codon is a sequence of three nucleotides on mRNA that codes for a specific amino acid or a stop signal during translation.

  • What is the start codon and what amino acid does it code for?

    The start codon is AUG and it codes for the amino acid methionine (Met).

  • What are stop codons and name them?

    Stop codons signal the end of translation. They are UAA, UAG, and UGA.

  • What is the role of tRNA in translation?

    tRNA carries specific amino acids to the ribosome and has an anticodon that base pairs with the mRNA codon.

  • How does the tRNA anticodon interact with mRNA codon?

    The tRNA anticodon is antiparallel and complementary to the mRNA codon, allowing hydrogen bonding between bases.

  • What are the three binding sites on a ribosome for tRNA during translation?

    The ribosome has three sites: A (aminoacyl), P (peptidyl), and E (exit) sites for tRNA binding and movement.

  • What happens during the initiation phase of translation?

    The small ribosomal subunit binds mRNA and initiator tRNA at the start codon, then the large subunit joins to form the initiation complex.

  • Describe the elongation phase of translation.

    During elongation, tRNAs bring amino acids to the ribosome, peptide bonds form between amino acids, and the ribosome moves along mRNA codon by codon.

  • What occurs during termination of translation?

    When a stop codon enters the A site, release factors bind, causing the polypeptide to be released and the ribosome to disassemble.

  • What is a polyribosome (polysome)?

    A polyribosome is a complex of multiple ribosomes simultaneously translating a single mRNA molecule.

  • How many amino acids are specified by the genetic code?

    The genetic code specifies 20 common amino acids.

  • Is the genetic code redundant or ambiguous?

    The genetic code is redundant (multiple codons can code for the same amino acid) but not ambiguous.

  • What is the difference between the template and coding strands of DNA in transcription?

    The template strand is used by RNA polymerase to synthesize mRNA, which is complementary and antiparallel; the coding strand has the same sequence as mRNA (except T instead of U).

  • What is the function of aminoacyl tRNA synthetase?

    Aminoacyl tRNA synthetase is an enzyme that charges tRNA by attaching the correct amino acid to its corresponding tRNA.

  • How is the polypeptide chain synthesized directionally?

    Polypeptides are synthesized from the N-terminus to the C-terminus during translation.

  • What is the significance of the 5’ cap and poly-A tail on mRNA?

    The 5’ cap and poly-A tail protect mRNA from degradation and assist in translation initiation and stability.

  • What is the role of ribosomal RNA (rRNA) in translation?

    rRNA forms the core of the ribosome's structure and catalyzes peptide bond formation as a ribozyme.

  • How do proteins destined for secretion or membranes differ in synthesis location?

    Proteins destined for secretion or membranes are synthesized on ribosomes bound to the rough endoplasmic reticulum (RER), while others are made on free ribosomes in the cytoplasm.