BIO142 lecture_Gene_rev_Genome Structure

Page 1: Genes & The Central Dogma

  • What is a gene?

    • A gene is a segment of DNA that contains the instructions for making a particular protein or set of proteins.

    • Genes play a critical role in heredity and the functioning of all living organisms.

  • What does it need to work?

    • Genes require several elements to function:

      • A regulatory element to control when and how often they are expressed.

      • Necessary transcription factors to initiate transcription.

      • An appropriate template (DNA) for RNA polymerization.

Page 2: Overview of Transcription and Translation

  • mRNA Production

    • mRNA is synthesized in the nucleus through several processes that transform the initial DNA information into a functional molecule.

  • Steps involved:

    1. Chromatin remodeling - Opening up DNA for access.

    2. Transcription - Synthesis of primary RNA transcript from DNA.

      • Chromatin exists as a DNA-protein complex; open chromatin allows access to RNA polymerase.

    3. RNA Processing - Modifications (5' cap, poly-A tail) are added to pre-mRNA, transforming it into mature mRNA.

    4. mRNA Stability - Regulation of mRNA lifespan in the cytoplasm.

    5. Translation - Ribosomes convert mRNA sequences into proteins through polymerization of amino acids.

    6. Post-translational modifications - Further modifications such as folding, glycosylation, and activation happen after translation, affecting protein function.

Page 3: Translation Process

  • Translation Defined

    • The process in which the sequence of nucleotides in mRNA is translated into a sequence of amino acids to form a protein.

  • Role of Ribosomes

    • Ribosomes catalyze the translation process:

      • Step a: mRNAs are exported from the nucleus to the cytoplasm.

      • Step b: Ribosomes read the mRNA and synthesize polypeptides, elongating the chain of amino acids via peptide bonds.

Page 4: Transcription Template

  • Transcription Overview

    • Involves reading the DNA template to synthesize RNA, with distinct strands:

      • Sense (Coding) strand

      • Non-template (Antisense) strand

  • Template strand: Serves as the pattern for RNA synthesis.

Page 5: Introduction to Transcription

  • What is Transcription?

    • The process of creating mRNA from a gene sequence, critical for gene expression.

Page 6: Requirements for Transcription

  • Necessary Elements:

    • Template: DNA strand to guide synthesis.

    • Initiation: Requires various steps, including strand separation and the triggering of RNA polymerase activity.

    • Termination: Signal to stop RNA synthesis once the gene has been fully transcribed.

Page 7: Holoenzyme Structure

  • Holoenzyme Composition

    • RNA polymerase combined with sigma factors forms a holoenzyme that initiates transcription by recognizing promoter regions.

    • Core enzyme (RNA polymerase) elongates mRNA after initiation.