1. Introduction

DNA and genetics are the foundation of biological inheritance, controlling how traits are passed from one generation to the next. They underpin the diversity and complexity of life, from bacteria to humans.

2. What is DNA?

Deoxyribonucleic Acid (DNA) is a molecule composed of two long strands forming a double helix. Each strand is made of nucleotides, which consist of a sugar, a phosphate group, and a nitrogenous base (adenine [A], thymine [T], cytosine [C], guanine [G]).

Diagram:
DNA Double Helix

Key Features:

  • DNA stores genetic instructions for growth, development, and functioning.
  • The sequence of bases encodes information.
  • Complementary base pairing: A-T, C-G.

3. Genes and Genomes

A gene is a segment of DNA that codes for a specific protein or functional RNA. The genome is the complete set of DNA in an organism.

Human Genome:

  • ~20,000 protein-coding genes
  • 3.2 billion base pairs

Diagram:
Gene Structure

4. Historical Context

  • 1866: Gregor Mendel discovers inheritance patterns in pea plants, founding genetics.
  • 1953: James Watson and Francis Crick describe the double helix structure of DNA.
  • 1977: First DNA sequencing methods developed.
  • 2003: Completion of the Human Genome Project.

5. How Genetics Works

  • Replication: DNA copies itself before cell division.
  • Transcription: DNA is converted to messenger RNA (mRNA).
  • Translation: mRNA guides protein synthesis at ribosomes.

Diagram:
Central Dogma

6. Inheritance Patterns

  • Mendelian: Dominant/recessive traits (e.g., eye color)
  • Polygenic: Multiple genes contribute (e.g., height)
  • Epigenetics: Chemical modifications to DNA affect gene expression without changing sequence

7. Surprising Facts

  1. The human brain has more connections than there are stars in the Milky Way.
    Estimated at over 100 trillion synapses, compared to 100–400 billion stars.

  2. Over 8% of human DNA comes from ancient viruses.
    These viral sequences, called endogenous retroviruses, have shaped evolution.

  3. Humans share 60% of their genes with bananas.
    This highlights the deep evolutionary connections across life.

8. Latest Discoveries

  • CRISPR-Cas9 and Prime Editing:
    Advanced genome editing tools allow precise DNA modifications, revolutionizing genetic medicine.

  • Epigenetic Inheritance:
    Studies show that environmental factors (diet, stress) can alter gene expression in offspring, even without DNA sequence changes.

  • Human Pangenome Project (2023):
    Researchers created a reference genome representing human diversity, revealing millions of previously unknown genetic variants.
    Reference: β€œA draft human pangenome reference” – Nature, 2023.

  • Brain Genomics:
    Recent research links specific genetic variants with neural connectivity patterns, advancing understanding of neurodevelopmental disorders.

9. Glossary

  • Allele: Variant form of a gene.
  • Chromosome: DNA molecule with part/all of the genetic material.
  • Epigenetics: Study of heritable phenotype changes not involving DNA sequence.
  • Genome: Complete set of genes or genetic material.
  • Mutation: Change in DNA sequence.
  • Nucleotide: Building block of DNA/RNA.
  • Phenotype: Observable traits of an organism.
  • Transcription: Process of making RNA from DNA.
  • Translation: Protein synthesis from mRNA.

10. References

11. Unique Insights

  • DNA is not static; it is constantly repaired and modified.
  • Genetic information flows from DNA to RNA to protein, but feedback loops exist.
  • The complexity of genetic regulation rivals the complexity of the universe itself.

End of Study Notes