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What are gene superfamilies? Explore huge gene clusters with hundreds of genes!
In modern genomics research, the concept of gene family is not only fascinating, but also an important key to understanding the complexity of life. A gene family is composed of several similar genes that are duplicated from a single original gene and usually have similar biochemical functions. Taking the human heme subgenes as an example, we can see that the ten genes are divided into two clusters, which exist on different chromosomes and are called α-heme and β-heme loci. The formation of these two gene clusters is thought to be the result of a gene duplication event about 500 million years ago.
Genes are grouped into families based on shared nucleotide or protein sequences.
Changes in gene families may be affected by random events on the one hand, and may also be the result of natural selection on the other. The expansion or contraction of these families often makes it difficult for researchers to distinguish the reasons behind them. Recent studies have combined statistical models and algorithmic techniques to identify gene families that are affected by natural selection.
Gene family structure
The composition and structure of genes provide a diverse background for gene families. Members of a gene family can be either paralogs or orthologs. Paralogous genes are genes with similar sequences within the same species, whereas orthologous genes are genes that retain similar sequences between different species. These gene families vary greatly in size, sequence diversity, and arrangement.
Due to the similarity and overlap in function of these gene sequences, individual genes within a family often share regulatory elements.
Members of some gene families have almost identical sequences, making it possible to express large amounts of gene products in a short period of time. Gene families sometimes also contain pseudogenes, which are DNA sequences that are similar to established gene sequences but are not functional. The existence of pseudogenes reveals many complexities in the process of gene evolution.
Gene family formation
Gene families form from multiple duplications of ancestral genes, followed by mutation and diversification. Duplications can occur within a lineage or as a result of divergence between species. This process can lead to the expansion of gene families; for example, humans and chimpanzees may have 15 copies of a gene derived from a common ancestor.
Repetitive Mechanism
In the formation of gene families, there are multiple levels of duplication, including exon duplication, whole gene duplication, and whole genome duplication. Whole genome duplication would double the number of copies of each gene and gene family.
Gene expansion often occurs through uneven crossover events during meiosis of germ cells.
These processes, coupled with gene relocation, allow gene members to coexist on many different chromosomes, further increasing genetic diversity.
Gene mutation
Mutations can result in amino acid substitutions through nonsynonymous mutations, which allow duplicate versions of a gene to acquire new functions without harming the organism. This mutation allows genes to expand in response to environmental pressures, just as organisms adapt to their external environment.
Evolution of gene families
During the evolution of genomes, gene families have demonstrated their huge role in biodiversity and evolution. Some genes may become disabled due to environmental changes, while others may be preserved due to beneficial mutations. For example, when environmental stress is intense, the expansion of genes helps species better adapt to the changes. Conversely, the contraction of a gene family is often accompanied by the accumulation of loss-of-function mutations.
Classification of functional families
In addition to structural classification based on evolution, HGNC also classifies based on gene function, forming a multi-level naming system. Although some genes do not have a direct evolutionary relationship, they may be classified into the same group because they perform similar functions. This is particularly evident in cancer gene research.
In summary, gene superfamily is not only an extension of the basic unit of organisms, but also indicates the key role of genes in dominating biodiversity and its evolution. So, as genomics develops further, how will the importance of gene families affect our understanding of life?
