Lecture Notes: DNA Structure and Central Dogma of Biology

Overview of DNA Structure and Function

• DNA as a Blueprint
  • DNA is likened to a blueprint which contains information for building a cell.
  • Cells are composed of nucleic acids, carbohydrates, lipids, and proteins.
  • Proteins serve as cell structures and enzymes that synthesize lipids, carbohydrates, and nucleic acids.

Key Concepts in DNA Functionality

• Process of DNA Replication

  • DNA replication produces two DNA molecules from one, ensuring each daughter cell receives a full DNA copy during cell division.

• DNA to Protein

  • The conversion of DNA information into proteins involves the processes of transcription and translation.

Transcription and Translation

• Transcription

  • DNA is transcribed to RNA, specifically mRNA, by RNA polymerase.
  • Template Strand: The strand used to synthesize RNA.
  • Coding Strand: The complementary strand matching the RNA sequence (thymine replaced by uracil in RNA).

• Translation

  • Ribosomes translate mRNA into proteins by determining the sequence of amino acids.
  • Example: Methionine, isoleucine, serine are amino acids coded by mRNA codons.

Genetic Terminology

• Genotype vs. Phenotype
  • Genotype: The full set of genes an organism possesses.
    • Example: Inherited genes for blood types (e.g., AO genotype results in A phenotype).
  • Phenotype: Observable traits resulting from genotype (e.g., blood type).

Bacterial Genomes and Gene Mapping

• Bacterial Chromosome

  • E. coli example shown in microscopy; nucleic acid is enclosed within the nucleoid.
  • Gene Mapping: Identifying gene locations and functions within bacterial genomes.
  • Functional genes include those for enzymes like superoxide dismutase, catalase (indicative of aerobic respiration), and proteins for flagella and chemotaxis.

• Gene Sequencing in Bacteria

  • Entire genomes can be sequenced to identify specific functions and differences between strains (e.g., benign E. coli vs. pathogenic strains causing kidney damage).

Central Dogma of Biology

• DNA -> RNA -> Protein
  • Known as the central dogma, describing the flow of genetic information within a biological system.
  • DNA Replication: DNA polymerase makes new strands.
  • RNA Transcription: RNA polymerase transcribes DNA to RNA.
  • Protein Synthesis: Ribosomes translate RNA to build proteins, essential for cellular structure and function.

Additional Visual Aids

• Animations depict the processes of transcription and translation for better understanding.