protein synth Flashcards
(13 cards)
What is the central dogma of molecular biology? (3 marks)
A:
Flow of Information: DNA → RNA → Protein.
Replication: Copies DNA for cell division.
Transcription: Synthesizes RNA from a DNA template.
Translation: Synthesizes polypeptides from RNA instructions.
What is transcription, and what are its key steps? (4 marks)
A:
Definition: Synthesizing an RNA sequence from a DNA template.
Key Enzyme: RNA polymerase:
Unwinds DNA by breaking hydrogen bonds.
Covalently joins complementary RNA nucleotides (Uracil replaces Thymine).
Steps:
RNA polymerase binds to the promoter region.
DNA strands separate, exposing the template strand.
RNA is synthesized based on complementary base pairing.
RNA transcript detaches and moves to the cytoplasm.
Q: What types of RNA are produced during transcription? (3 marks)
A:
mRNA: Carries genetic instructions.
tRNA: Brings amino acids to ribosomes.
rRNA: Catalyzes peptide bond formation.
How is transcription regulated? (2 marks)
A:
Transcription Factors: Control RNA polymerase activity.
Genes can be switched ‘on’ or ‘off’ based on cellular needs.
What is translation, and what are its key components? (4 marks)
A:
Definition: Converts mRNA instructions into a polypeptide chain.
Key Components:
mRNA: Contains codons specifying amino acids.
tRNA:
Anticodon pairs with mRNA codon.
Carries specific amino acids.
Ribosomes:
Small subunit binds mRNA.
Large subunit holds tRNA and forms peptide bonds.
Q: What are the steps of translation? (5 marks)
A:
Initiation:
Small ribosomal subunit binds mRNA at start codon (AUG).
Initiator tRNA (Met) binds to AUG.
Large ribosomal subunit joins the complex.
Elongation:
Ribosome moves along mRNA, reading codons.
tRNA anticodons pair with mRNA codons, adding amino acids.
Peptide bonds form between amino acids via condensation reactions.
Termination:
Ribosome reaches a stop codon (UAA, UAG, UGA).
Release factors disassemble the ribosomal complex and release the polypeptide.
What are the post-transcriptional modifications, and why are they important? (3 marks)
Q: What are the post-transcriptional modifications, and why are they important? (3 marks)
A:
Capping: Addition of a 5′ cap for protection and ribosome binding.
Polyadenylation: Addition of a poly-A tail to the 3′ end for stability.
Splicing: Removal of introns and joining of exons.
Alternative Splicing: Produces multiple protein variants from a single gene.
Q: What are the key characteristics of the genetic code? (3 marks)
A:
Universal: Same codons specify the same amino acids across organisms.
Degenerate: Multiple codons can encode the same amino acid.
Non-Overlapping: Codons are read sequentially without overlap.
What are codons, and what roles do they play in translation? (2 marks)
A:
Codons: Triplets of bases specifying an amino acid.
Roles:
Start codon (AUG) signals the beginning of translation.
Stop codons (UAA, UAG, UGA) terminate translation.
What happens during protein folding and post-translational modifications? (3 marks)
A:
Folding: Polypeptide chains fold into specific 3D structures to become functional proteins.
Post-Translational Modifications:
Phosphorylation: Activates proteins or signaling pathways.
Glycosylation: Adds sugar molecules to direct proteins to specific locations.
Cleavage: Removes sections of the polypeptide to activate proteins.
What types of mutations can occur during protein synthesis, and what are their impacts? (3 marks)
A:
Point Mutation: Single base change (e.g., Sickle cell anemia: GAG → GUG).
Frameshift Mutation: Insertion or deletion altering the reading frame.
Impact: May result in nonfunctional or harmful proteins.
How is protein synthesis applied in science and technology? (3 marks)
A:
Medical Research: Understanding genetic diseases and developing targeted therapies.
Biotechnology: Producing recombinant proteins like insulin.
Forensics: DNA profiling and genetic analysis.
