1. What is DNA?

DNA (Deoxyribonucleic Acid) is the molecule that stores genetic information in all living organisms.

  • Structure: Double helix with two strands made of nucleotides (Adenine, Thymine, Cytosine, Guanine).
  • Function: Encodes instructions for protein synthesis and cellular functions.

DNA Double Helix

2. Genes and Chromosomes

  • Gene: A segment of DNA that codes for a specific protein.
  • Chromosome: DNA packaged with proteins; humans have 23 pairs.
  • Genome: Entire set of genetic material in an organism.

3. How Genetics Works

Central Dogma

  1. Replication: DNA copies itself.
  2. Transcription: DNA → RNA.
  3. Translation: RNA → Protein.

Mendelian Inheritance

  • Dominant and Recessive Alleles: Traits are determined by allele combinations.
  • Genotype vs. Phenotype: Genotype is genetic makeup; phenotype is observable traits.

4. Bioluminescent Organisms

  • Definition: Organisms that produce light via chemical reactions.
  • Genetic Basis: Genes encode enzymes (luciferase) and substrates (luciferin) for bioluminescence.
  • Ecological Role: Communication, predation, camouflage.

Bioluminescent Waves

5. Surprising Facts

  1. Human DNA is 99.9% identical between individuals—the 0.1% accounts for all genetic diversity.
  2. Some bacteria can transfer genes directly to other species (horizontal gene transfer), accelerating evolution.
  3. Bioluminescence has evolved independently at least 40 times across different life forms (Johnsen et al., 2020).

6. Recent Research

  • 2020 Study: Johnsen et al. (Science, 2020) revealed the genetic diversity of bioluminescent mechanisms in marine organisms, showing that gene clusters responsible for light production are highly variable and have evolved multiple times independently.

7. Ethical Considerations

  • Genetic Privacy: Protecting individuals’ genetic data from misuse.
  • Gene Editing (CRISPR): Balancing medical advances with potential risks (e.g., designer babies, ecological impacts).
  • Bioluminescence Applications: Ethical sourcing and environmental impact of using bioluminescent genes in research and biotechnology.

8. Memory Trick

“A Tall Cat Grows”

  • Adenine pairs with Thymine
  • Cytosine pairs with Guanine

9. Common Misconceptions

  • DNA is not the same as a gene: DNA is the molecule; genes are specific sequences within DNA.
  • Genes do not determine destiny: Environment and gene interactions affect traits.
  • Bioluminescence is not always blue or green: It can range from red to violet, depending on the organism.

10. Diagram: Central Dogma

Central Dogma

11. Unique Insights

  • Epigenetics: Chemical modifications to DNA (e.g., methylation) can turn genes on/off without changing the sequence.
  • Non-coding DNA: Over 98% of human DNA does not code for proteins but plays regulatory roles.
  • Genetic Engineering: Bioluminescent genes from jellyfish have enabled tracking of gene expression in medical research.

12. Glossary

  • Allele: Variant form of a gene.
  • Mutation: Change in DNA sequence.
  • Phenotype: Observable characteristics.
  • Genotype: Genetic makeup.

13. References

  • Johnsen, S., et al. (2020). “The diversity and evolution of marine bioluminescence.” Science, 368(6490), 1172-1175. Link
  • National Human Genome Research Institute. “What is DNA?” Link

14. Summary Table

Concept Description Example
DNA Genetic material Double helix structure
Gene DNA segment coding for protein Eye color gene
Chromosome DNA/protein package Human chromosome 1
Bioluminescence Light production by organisms Jellyfish, plankton
Epigenetics DNA modifications affecting gene expression DNA methylation

15. Quick Review Questions

  1. What are the four DNA bases?
  2. How does bioluminescence occur genetically?
  3. Name one ethical concern in genetics.

End of Notes