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DNA Replication, Transcription, Translation and Central Dogma

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  • Central Dogma of Molecular Biology

    The flow of genetic information from DNA to RNA to protein.

  • Chargaff's Rules

    In any species, the amount of Adenine (A) equals Thymine (T), and the amount of Guanine (G) equals Cytosine (C).

  • Base Pairing in DNA

    Purines (A and G) pair with pyrimidines (T and C) to maintain consistent DNA width: A-T and G-C pairs.

  • Difference between DNA and RNA bases

    DNA has Thymine (T), RNA has Uracil (U) instead of thymine.

  • DNA Structure

    DNA is a double helix with a sugar-phosphate backbone and nitrogenous bases paired by hydrogen bonds.

  • DNA Replication Model

    Replication is semiconservative: each daughter DNA molecule has one parental and one new strand.

  • Origin of Replication

    Specific sites where DNA strands separate to start replication; eukaryotes have multiple origins, prokaryotes usually one.

  • Replication Bubble and Fork

    The replication bubble is the unwound region; replication forks are the Y-shaped regions where new DNA strands elongate.

  • Key Enzymes in DNA Replication

    Helicase unwinds DNA, Primase makes RNA primers, DNA polymerase synthesizes new DNA, SSB proteins stabilize strands.

  • Leading vs Lagging Strand

    Leading strand is synthesized continuously; lagging strand is synthesized discontinuously as Okazaki fragments.

  • Role of DNA Ligase

    DNA ligase joins Okazaki fragments by forming phosphodiester bonds to complete lagging strand synthesis.

  • Transcription Process

    DNA is transcribed into pre-mRNA, which is processed into mature mRNA by capping, polyadenylation, and splicing.

  • RNA Splicing

    Introns are removed and exons are joined to form mature mRNA; splicing is catalyzed by spliceosomes.

  • Functional Importance of Introns

    Introns allow alternative splicing, increasing protein diversity and have evolutionary significance.

  • Translation Stages

    Translation has three stages: initiation, elongation, and termination.

  • Role of tRNA in Translation

    tRNA carries specific amino acids and has an anticodon that base-pairs with mRNA codons.

  • Genetic Code

    The genetic code is a dictionary of codons specifying amino acids; it is nearly universal and redundant.

  • Termination of Translation

    Occurs when a stop codon reaches the ribosome's A site; a release factor promotes polypeptide release.

  • Post-Translational Modifications

    Polypeptides often undergo modifications and are targeted to specific cellular locations to become functional proteins.