Molecular Biology Translation Quiz

Protein Synthesis (Translation)

• Protein synthesis, also known as translation, uses mRNA as a template to create proteins.
• Translation involves converting the nucleotide sequence of mRNA into the amino acid sequence of a protein, following the genetic code.
• The genetic code is a "dictionary" that specifies the correspondence between a sequence of nucleotide bases and a sequence of amino acids.
• Each "word" in the code consists of three nucleotides, called codons.
• Codons specify the type and position of amino acids in the protein.
• There are 64 possible codons, which code for 20 amino acids.
• AUG is a start codon and codes for methionine in eukaryotes and N-formylated methionine in prokaryotes.
• UAA, UAG, and UGA are stop codons.
• The genetic code is degenerate, meaning more than one codon can code for the same amino acid.
• The wobble hypothesis explains the degeneracy of the genetic code. Base pairing at the third position of a codon is not strict, allows for flexibility in the tRNA-mRNA interaction.
• Mutations are permanent changes in DNA sequence that lead to new hereditary variations and create a mutant gene.
• Mutations can cause different types of genetic diseases.
• Point mutations involve substitution of one base pair by another.
• Transition mutations involve a purine to purine or pyrimidine to pyrimidine substitution.
• Transversion mutations involve a purine to pyrimidine or pyrimidine to purine substitution.
• Silent mutations occur when a single nucleotide change results in the same amino acid being incorporated.
• Missense mutations result in a change in the amino acid sequence and cause changes in the protein function
• Nonsense mutations cause premature termination of protein chain due to a codon alteration.
• Frame-shift mutations result from insertion or deletion of bases, changing the reading frame and causing significant changes in the resulting protein.
• The synthesis requires components including ribosomes, mRNA, tRNA, amino acids, aminoacyl-tRNA synthetase, and energy sources (ATP and GTP).
• Ribosomes are complex structures composed of protein and rRNA, responsible for protein synthesis.
• tRNA carries amino acids to the ribosomes, pairing with the mRNA codons.
• Aminoacyl-tRNA synthetase attaches the correct amino acid to the tRNA, requiring ATP.
• The process of translation occurs in three stages: initiation, elongation, and termination.

Objectives of Protein Synthesis

• Recognition of the genetic code, how they specify the order of amino acids during protein synthesis.
• Identification of genetic code characters.
• Comparison between different types of DNA mutation and the resulting genetic diseases.
• Identification of requirements of protein synthesis including ribosomes, mRNA, amino acids, tRNA, aminoacyl-tRNA synthetase enzymes.
• Steps of protein synthesis (Translation): Activation, Initiation, Elongation, Termination.
• Examples of inhibitors of protein synthesis.
• Recognition of post-translational processing of proteins.

Steps in Protein Synthesis (Translation)

• Activation: Amino acids are activated by attaching to tRNA, using aminoacyl-tRNA synthetases.
• Initiation: mRNA, first tRNA with methionine, and the small ribosomal subunit assemble with initiation factors.
• Elongation: Ribosome moves along the mRNA, adding amino acids to the growing polypeptide chain.
• Termination: A stop codon is reached, polypeptide chain release, and ribosome subunits dissociate.
• Folding and Post-translational Processing: Newly synthesized proteins fold into their 3-D functional conformations, and undergo modifications.

Inhibitors of Protein Synthesis

• Streptomycin, Tetracycline, Chloramphenicol, Erythromycin, clindamycin, Puromycin, Ricin, Diphtheria toxin are examples of protein synthesis inhibitors.
• These agents disrupt various steps in translation, such as initiation complex formation, translocation, aminoacyl-tRNA binding, or peptidyl transferase activity.

Properties of the Genetic Code

• Unambiguous: Each codon specifies only one amino acid.
• Degenerate: Multiple codons can code for the same amino acid.
• Universal: The same codons specify the same amino acids in all organisms.
• Non-overlapping: Codons are read one after another without overlapping.
• Non-punctuated: No punctuation between codons.

Mutations

• Mutations can be point mutations (e.g., silent, missense, nonsense mutations) or frame-shift mutations (insertion or deletion).
• Mutations change the genetic code causing abnormal proteins, diseases, and in some cases, evolutionary changes.

Post-Translational Processing

• Modifications of newly synthesized proteins after translation.
• Examples: Trimming (removal of parts of the polypeptide chain), covalent modifications (phosphorylation, glycosylation, acetylation, hydroxylation, carboxylation), folding, and quaternary structure assembly.

Requirements of Protein Synthesis

• Ribosomes (protein synthesizing machinery)
• mRNA (carries genetic code)
• Amino acids (building blocks)
• tRNA (carries amino acids to ribosomes)
• ATP (energy source)
• GTP (energy source)
• Aminoacyl-tRNA synthetases (link amino acids to tRNA)
• Protein factors (facilitate ribosome-mRNA and tRNA interactions)

Test your knowledge on the translation process in molecular biology. This quiz covers key concepts like codons, mRNA function, tRNA roles, and mutations. Assess your understanding of protein synthesis and its mechanisms.