Q: Why do Okazaki fragments occur during DNA replication?
A: Because the lagging strand is oriented opposite to the direction DNA polymerase can follow the replication fork (DNA pol works 5′ → 3′ only).
Q: What does it mean that SSB proteins prevent annealing?
A: They keep the separated DNA strands from re-pairing so replication can continue.
Q: Why is DNA replication described as semi-conservative?
A: Each daughter DNA molecule contains one parental strand and one newly synthesized strand.
Q: In nucleic acids, how are nitrogenous bases linked together in the polymer?
A: By phosphodiester bonds linking the sugar of one nucleotide to the phosphate of the next.
Q: What is the function of a gene promoter?
A: It provides a binding site for the transcription initiation complex, including RNA polymerase.
Q: Why are specific transcription factors important in multicellular eukaryotes?
A: They ensure that only genes relevant to a cell’s identity and function are expressed.
Q: Why are mitotic chromosomes transcriptionally inactive?
A: DNA is highly condensed, so transcription machinery cannot access genes.
Q: How does the cell ensure proteins needed for mitosis are ready if transcription stops during mitosis?
A: Proteins are synthesized during G2 before mitosis begins.
Q: What does wobble pairing allow during translation?
A: One tRNA anticodon to pair with multiple codons, reducing the number of tRNAs needed.
Q: Why are mutations in the tryptophan (Trp) codon especially severe?
A: Trp is encoded by only one codon, so mutations cannot be silent.
Q: Which mutation is most likely to prevent formation of a functional protein?
A: A mutation that removes or alters the start codon (ATG).
