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The mystery of the gene family: How did humans change from a single gene to a diverse gene family?
Scientists' research on genes shows that a gene family is composed of multiple similar genes, which are formed by the duplication of a single original gene and usually have similar biochemical functions. For example, human hemoglobin subunit genes are one of the well-known gene families, and these ten genes are distributed on different chromosomes, called α-globin and β-globin loci. The two gene clusters are thought to have arisen from the duplication of a precursor gene about 500 million years ago.
The expansion or contraction of a gene family can be the result of randomness or the result of natural selection; however, distinguishing between the two is very difficult in practical applications.
How do gene families form in the face of such changes? Gene families arise from multiple duplications of an ancestral gene, which subsequently undergo mutation and divergence. These duplications can occur within a lineage, for example humans may have two copies of a gene that only appeared once in chimpanzees, or through genetic duplication in speciation.
The process of translating an entire gene can involve four levels of duplication: exome duplication and splicing, whole gene duplication, multigene family duplication, and whole genome duplication. When two chromosomes are misaligned, a crossover recombination event occurs, causing one chromosome to have an increased number of genes and the other to have a decreased number of genes. Such gene clusters expand and eventually form larger gene families.
There are close similarities in the genes of the common ancestor of humans and chimpanzees, which shows how gene families evolve.
In addition to duplication, the diversity of genes after mutation ultimately leads to different functions and expression levels. Another reason for this diversity is non-synonymous mutations within genes, which allow duplicate gene copies to acquire new functions without causing excessive negative effects on the organism.
Some multigene families are very homogeneous, with the sequences of their gene members being almost identical, a phenomenon known as "coevolution."
Gene families play important roles in evolution and diversity. Over time, gene families continue to expand and shrink, and genes within the family will replicate and differentiate into new genes, and may also face the risk of being lost. Such dynamic processes allow organisms to adapt to changes in the external environment.
Based on the functional classification, the HUGO Gene Nomenclature Committee (HGNC) has also developed a naming method for gene families. These names not only depend on the structure, but are also closely related to the function of the gene. For example, the BRCA1 and BRCA2 genes, which are associated with breast cancer, are not related but are grouped together based on their common functions.
In summary, gene family is a very complex and fascinating organizational level in the human genome, which affects the evolution and diversity of life. Are there any unknown evolutionary stories hidden behind these gene families?
