How are Genes Made?

January 14, 2025

Recent studies have advanced our understanding of gene evolution and function. In December 2024, two prominent research groups published findings that shed light on how new genes are created. One group from the University of Nevada, Reno, reported in *Molecular Biology and Evolution*, while the other from the Max Planck Institute for Evolutionary Biology in Germany published in *Genome Biology and Evolution*. These studies explored gene duplication, methylation, and the role of random DNA sequences in evolution.

Genes and Chromosomes

Genes are segments of DNA that determine the characteristics of an organism. Humans possess 24 chromosomes, which include 22 numbered chromosomes and two sex chromosomes (X and Y). Each person inherits one set of chromosomes from each parent, resulting in two copies of each chromosome. Identical twins originate from a single zygote, while non-identical twins arise from separate zygotes.

DNA Structure and Function

Each DNA molecule consists of two strands connected by base pairs. The human genome comprises approximately 3.2 billion base pairs, with about 20,000 protein-coding genes. Genes are expressed when the DNA sequence is transcribed into messenger RNA (mRNA), which guides protein synthesis. Additionally, genes known as promoters and enhancers regulate when and where other genes are expressed.

Gene Duplication as a Source of New Genes

Japanese-American biologist Susumu Ohno proposed in 1970 that gene duplication is a primary source of new genes. This process allows one copy of a gene to maintain its original function while the other can mutate and develop new functions. Recent research from the University of Nevada, Reno, revealed that duplicated genes exhibit higher levels of methylation, which prevents excessive protein production and enables the survival of duplicate genes.

Exogenous DNA and Random Sequences

The Max Planck Institute team inserted exogenous DNA into human-derived cells to study the effects of random base-pair sequences on cell growth. After 20 days, they observed that 53% of cell types became less abundant, while 8% increased. This indicates that random DNA sequences can influence cell characteristics and may act as incipient genes in evolution.

The Complexity of Gene Utility

For a gene to be retained in a genome, it must provide some utility or be allowed to mutate. Determining a gene’s usefulness can be challenging. For example, blood types are determined by variants of the ABO gene. Individuals can have blood types A, B, AB, or O, depending on the inherited gene variants. Notably, the O variant encodes a protein with no known function, denoting the complexities of gene retention in evolution.

Exogenous DNA refers to genetic material from external sources.
Susumu Ohno’s hypothesis on gene duplication laid the groundwork for modern genetics.
Methylation is a chemical modification that can influence gene expression.
Incipient genes are newly formed genes that may arise from random DNA sequences.
The ABO blood group system illustrates gene variation without essentiality.

Evolutionary Implications of Gene Retention

About how genes evolve and are retained within genomes offers vital information about biological diversity. The mechanisms of gene duplication, methylation, and the impact of random sequences illustrate the complexity of genetic evolution. These findings contribute to the broader understanding of genetic variation and its implications for species adaptation and survival.

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