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Microbial Genetics: DNA Replication, Transcription, and Translation

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  • What is the central dogma of molecular biology?

    The flow of genetic information from DNA to RNA (transcription) and then to protein (translation).

  • What is the structure of bacterial chromosomes?

    Bacteria usually have a single circular chromosome made of DNA and associated proteins, often supercoiled.

  • What does it mean that DNA strands are antiparallel?

    The two DNA strands run in opposite directions: one strand runs 5' to 3', the other 3' to 5'.

  • What is the role of helicase in DNA replication?

    Helicase unwinds the double-stranded DNA helix, separating the strands to form the replication fork.

  • How is the leading strand synthesized during DNA replication?

    The leading strand is synthesized continuously in the 5' to 3' direction by DNA polymerase, starting from an RNA primer.

  • What are Okazaki fragments?

    Short DNA fragments synthesized discontinuously on the lagging strand during DNA replication.

  • What enzymes join Okazaki fragments?

    DNA polymerase removes RNA primers and DNA ligase joins the Okazaki fragments covalently.

  • What provides the energy for DNA replication?

    Hydrolysis of the phosphate bonds of nucleoside triphosphates (dNTPs) provides energy for DNA synthesis.

  • What is the function of DNA gyrase (topoisomerase) during replication?

    Relaxes supercoiling ahead of the replication fork to prevent DNA tangling.

  • What is transcription?

    The synthesis of a complementary mRNA strand from a DNA template.

  • What is the role of RNA polymerase in transcription?

    RNA polymerase binds to the promoter and synthesizes RNA in the 5' to 3' direction using DNA as a template.

  • What are the three stages of transcription?

    Initiation: RNA polymerase binds promoter; Elongation: RNA strand is synthesized; Termination: RNA polymerase stops at terminator sequence.

  • What is the difference between prokaryotic and eukaryotic transcription?

    Eukaryotic transcription occurs in the nucleus and involves a TATA box and multiple transcription factors; prokaryotic transcription occurs in the cytoplasm without introns.

  • What are exons and introns?

    Exons are coding regions of genes; introns are noncoding regions removed during mRNA processing in eukaryotes.

  • What is translation?

    The process of synthesizing proteins by decoding mRNA codons into amino acids.

  • What is a codon?

    A sequence of three mRNA nucleotides that codes for a specific amino acid or a stop signal.

  • What is the start codon for translation?

    AUG is the start codon and codes for methionine.

  • What are the stop codons in translation?

    UAA, UAG, and UGA signal termination of translation.

  • What is the role of tRNA in translation?

    tRNA transports amino acids to the ribosome and has an anticodon that base-pairs with mRNA codons.

  • How are amino acids joined during translation?

    Amino acids are joined by peptide bonds to form a growing polypeptide chain.

  • What is simultaneous transcription and translation in bacteria?

    In bacteria, translation can begin on mRNA while transcription is still in progress due to lack of nuclear membrane.