Lecture Notes: Central Dogma of Biology

Overview

• DNA as a Blueprint:
  • DNA contains information for building cells.
  • Cells are composed of nucleic acids, carbohydrates, lipids, and proteins.
  • Proteins serve as structural components and enzymes.

DNA Replication

• DNA replication results in two DNA molecules from one parent DNA.
• Each new DNA molecule ends up in a daughter cell post-cell division.

Key Processes

• Transcription:

  • Information in DNA is used to produce RNA via RNA polymerase.
  • Transcription results in messenger RNA (mRNA).

• Translation:

  • Process where ribosomes read mRNA to build proteins.
  • mRNA sequence dictates amino acid order in proteins.

DNA, Genotype, and Phenotype

• Genotype:

  • Refers to all genes in an organism.
  • Includes coding genes and non-coding regions.
  • Example: Human genotype derived from parental genes (e.g., type O and type A blood genes).

• Phenotype:

  • Observable traits resulting from the genotype (e.g., blood type A).

Bacterial Genome Mapping

• Gene Mapping:
  • Mapping involves identifying new genes and their functions on bacterial genomes.
  • Example genes: Superoxide dismutase (oxygen tolerance), flagella formation, chemotaxis, adhesion.
• Gene Sequencing:
  • Identification and differentiation of bacterial strains based on gene presence and function.
  • Example: Differentiating E. coli strains based on toxin-encoding genes.

Central Dogma of Biology

• Concept: DNA > RNA > Protein.

• DNA replication involves enzymes for copying information.

• Transcription:

  • DNA information transcribed to RNA.
  • Template strand used for mRNA synthesis.
  • Coding strand remains complementary.

• Translation:

  • mRNA guides protein synthesis at ribosomes.
  • Codons in mRNA (e.g., AUG, AUC, UAA) specify amino acids and start/stop signals.

Detailed Transcription Process

• DNA Structure: Double helix unwinds only at gene sites.
• mRNA Synthesis:
  • Template strand produces mRNA matching coding strand with uracil replacing thymine in RNA.
  • Example transcription: DNA sequence TAG -> RNA sequence AUC.

Translation Process

• Ribosome Function:
  • Reads mRNA to assemble proteins.
  • Initial amino acids determined by first codons in mRNA (e.g., methionine, isoleucine, serine).
• mRNA Movement:
  • In eukaryotes, mRNA exits nucleus to cytoplasm for translation.
  • In prokaryotes, transcription and translation occur in cytoplasm.

Visualization and Learning Aids

• Use animations to visualize transcription and translation.
• Clarification on template vs. coding strands and their roles in RNA synthesis.

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This lecture outlines the essential processes of how genetic information in DNA is used to synthesize proteins, emphasizing the central dogma, and provides an understanding of genotypic and phenotypic expressions in organisms.