Origin and Evolution of Genes

• Humans possess approximately 20,000 genes within their DNA.
• These genes encode the molecules composing the body, including keratin, collagen, and dopamine.
• Other species also possess unique genes, such as spider silk genes in spiders and chlorophyll genes in oak trees.

Origin of Genes

• Life on Earth is estimated to have begun around 4 billion years ago.
• Early life forms consisted of primitive microbes containing a basic set of genes essential for survival.
• These fundamental genes were passed down through generations.
• Some of these genes still serve similar functions in our cells today, such as DNA replication.
• However, these early microbes lacked genes for complex traits like spider silk or dopamine.

Gene Duplication and Mutation

• The diversity of genes on Earth has increased over time.
• Many new genes originated from errors during cell division, where DNA is copied.
• Accidental duplication of a DNA segment can result in an extra copy of a gene.
• Initially, the duplicated gene functions the same as the original.
• Over generations, mutations can accumulate in the extra gene, altering its function.
• Duplication of the mutated gene can also occur.
• A significant number of mutated genes have emerged relatively recently, some even after humans diverged from apes.
• It can take millions of years for a single gene to evolve into a family of genes.
• Once evolved, new genes can rapidly acquire essential functions.
• Humans possess hundreds of genes for odor receptor proteins in the nose.
• Mutations allow these proteins to bind to different molecules, enabling the perception of trillions of smells.

Functional Divergence

• Mutations can cause a gene to produce its protein in a different organ or at a different stage of life.
• The protein may also take on an entirely different function.
• In snakes, a gene that originally produced a bacteria-killing protein in the pancreas duplicated and mutated.
• This mutation caused the protein to be produced in the snake's mouth instead.
• The protein's harmful effect aided in prey capture, leading to its selection and evolution into venom.

De Novo Gene Creation

• The DNA of animals and plants contains vast stretches of non-coding sequences.
• These sequences are primarily random genetic material with no known function.
• Mutations within these non-coding regions can create new start sites for gene transcription.
• This can lead to the production of novel proteins.
• Initially, the protein may be useless or harmful.
• Further mutations can alter the shape and function of the protein.
• Eventually, the protein may acquire a beneficial function, enhancing the organism's health, strength, or reproductive success.
• Scientists have identified newly created genes functioning in various animal tissues.

Conclusion

• Our 20,000 genes have diverse origins.
• These include the origin of life and ongoing de novo gene creation.
• The process of creating new genes continues as long as life exists on Earth.