The Origin and Evolution of Genes

Introduction to Genes

• Human DNA consists of about 20,000 genes.
• Genes encode molecules essential for various body functions (e.g., keratin, collagen, dopamine).
• Different species have unique genes (e.g., spider silk in spiders, chlorophyll in oak trees).

Origin of Genes

• Life on Earth began approximately 4 billion years ago with primitive microbes.
• Early life forms had a basic set of genes for survival tasks.
• Some ancient genes are still active today (e.g., DNA replication).
• Newer genes (e.g., for spider silk or dopamine) have developed over time.

Gene Duplication and Mutation

• Genes can duplicate during cell division, creating extra copies.
• Mutations in duplicated genes can lead to new functions over generations.
• Many mutated genes have appeared in recent evolutionary history.
• New genes can emerge rapidly and acquire essential roles.

Examples of Gene Mutation

• Olfactory Genes: Humans have hundreds of genes for odor molecule proteins, allowing a wide range of smell perception.
• Snake Venom: A gene originally for antibacterial proteins in the pancreas duplicated and mutated to produce venom in the mouth, aiding prey capture.

Non-Coding DNA and New Genes

• Large stretches of DNA do not code for proteins and appear random.
• Mutations in non-coding DNA can create new gene sequences.
• New proteins may initially be useless but can evolve beneficial functions through further mutations.

Conclusion

• The 20,000 genes in humans have diverse origins, from ancient life forms to recent developments.
• Life on Earth continually evolves, creating new genes over time.