Molecular Biology Syllabus

Unit I: Introduction to Cell Biology and Genetics

I. Prokaryotic and Eukaryotic Cells

  • Definition of a Cell: Fundamental structural and functional unit of living organisms. It performs various functions such as digestion, respiration, and reproduction.

  • Types of Organisms:

    • Unicellular: Organisms made up of a single cell.

    • Multicellular: Organisms made up of multiple cells.

  • Classification: Based on the presence of a nucleus, cells are divided into prokaryotic and eukaryotic cells.

    • Prokaryotic Cells:

      • Simple, smaller, single-celled organisms (e.g., bacteria, cyanobacteria).

      • Lack a defined nucleus and membrane-bound organelles.

      • Typically reproduce asexually via binary fission.

      • Shapes: cocci (spherical), bacilli (rod-shaped), spirals (e.g. Treponema).

    • Eukaryotic Cells:

      • Larger and more complex than prokaryotic cells.

      • Contain a membrane-bound nucleus and various organelles.

      • Share common features with prokaryotic cells: plasma membranes, ribosomes, and DNA.

1. Structure of Prokaryotic Cells

  • Characteristics:

    • Smaller size (0.3 to 2 μm) compared to eukaryotic cells.

    • Simple internal organization and lack of organelles such as mitochondria and Golgi apparatus.

  • Bacterial Surface Layers:

    • Plasma Membrane: Thin, flexible layer controlling molecular movement; contains respiratory enzymes.

    • Cell Wall: Rigid structure made of peptidoglycan; thickness varies (1.5 to 100 μm); essential for bacterial classification.

    • Capsule: Gelatinous coat protecting bacteria against desiccation and immune responses.

2. Cytoplasm

  • Contains proteins, lipids, glycogen, inorganic ions, enzymes, ribosomes, tRNA, and mRNA.

  • Special Features:

    • Lacks organelles found in eukaryotes.

    • Ribosomes are smaller (70S) and free within the cytoplasm.

    • Gas vacuoles and polysaccharide deposits may be present.

3. Nucleoid

  • Genetic material is present within the cytoplasm as a circular DNA molecule (bacterial chromosome).

  • Lacks a nuclear envelope, non-coding regions (introns) and is haploid.

  • Continuous DNA replication occurs; transcription and translation occur simultaneously in the cytoplasm.

4. Plasmids

  • Circular DNA molecules that carry additional genes (e.g. antibiotic resistance).

  • Facilitate horizontal gene transfer amongst bacteria and contribute to the spread of antibiotic resistance.

5. Outer Flagella and Pili

  • Flagella: Central feature of motile bacteria; helps in movement.

  • Pili: Short, non-motile structures aiding in attachment to surfaces.

Structure of Eukaryotic Cells

  • More developed internal organization with membrane-bound organelles.

  • Key Characteristics:

    • Number: Varies with organism size, e.g., approx. 30 quadrillion cells in a human body.

    • Shape: Diverse shapes related to function; include spherical, cuboidal, disc-like forms.

    • Size: Generally between 10 to 100 μm.

Components of Eukaryotic Cells

  • Cell Membrane: Thin, elastic barrier, controlling material transfer, lacks respiratory enzymes.

  • Cytoplasm: Semi-fluid substance where metabolic processes occur; separates into ectoplasm and endoplasm in protozoans.

  • Nucleus:

    • Enclosed by nuclear envelope with pores; DNA organized into chromosomes.

    • Contains euchromatin (active) and heterochromatin (inactive).

  • Organelles:

    • Mitochondria: Double-membrane structures producing ATP.

    • Endoplasmic Reticulum (RER/SER): Network enabling protein and lipid synthesis.

    • Golgi Bodies: Modify and package proteins for transport.

    • Ribosomes: Site of protein synthesis, composed of rRNA and proteins.

    • Cilia and Flagella: Motility structures made of microtubules.

Unit II: Molecular Biology

I. Overview on Genome

  • Definition of Genome: All genetic material in a cell, comprising both coding and noncoding regions.

  • Bacterial Genomes: Typically 0.5–10Mb; features circular DNA with minimal non-coding sequences.

  • Human Genome: Contains 3 billion base pairs; organized into linear chromosomes.

II. Nucleic Acid Structure and Function

  • Nucleic Acids: Composed of nucleotides (phosphate, sugar, nitrogen bases). Key classes include DNA and RNA.

    • DNA: Double-stranded, self-replicating; encodes genetic information.

    • RNA: Single-stranded, involved in protein synthesis; includes mRNA, tRNA, and rRNA.

III. DNA Replication

  • Process: DNA replication is semi-conservative involving multiple enzymes (e.g., helicase, DNA polymerase).

  • Strands: Leading strand synthesizes continuously; lagging strand synthesizes discontinuously (Okazaki fragments).

IV. Transcription

  • Definition: Process of copying DNA into RNA; involves RNA polymerase.

  • Phases: initiation, elongation, termination.

V. Translation

  • Definition: Decoding mRNA into a polypeptide chain utilizing ribosomes and tRNA.

  • Process: Consists of initiation, elongation, and termination phases.

VI. Mutations, DNA Damage, and Repair Mechanisms

  • Types of Damage: Include deamination, mismatches, breaks, and crosslinks.

  • Repair Mechanisms: Base excision repair (BER), nucleotide excision repair (NER), and mismatch repair (MMR).

VII. Gene Transfer in Bacteria

  • Mechanisms: Conjugation, transformation, and transduction allow genetic material exchange.

VIII. Control of Gene Expression

  • Eukaryotic vs. Prokaryotic Regulation: More complex regulation in eukaryotes with nuclear membrane involvement.

IX. DNA Recombination

  • Types: Homologous recombination, non-homologous recombination, site-specific recombination.

X. DNA Sequencing Techniques

  • Sanger and NGS: Different methods for determining sequences of DNA.

XI. Microarrays

  • Purpose: Analyze gene expression and identify mutations using DNA chips.