How many genes are present in the human genome
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Estimating the Number of Genes in the Human Genome
Early Estimates of Human Gene Count
Initial estimates of the number of genes in the human genome varied widely. Early predictions suggested a range between 60,000 and 100,000 genes . However, subsequent analyses using expressed sequence tags (ESTs) and other methods provided a broader range of estimates, from as few as 45,000 to as many as 140,000 genes .
Lower Estimates from Genome Sequencing Projects
The completion of the human genome sequence brought more refined estimates. The sequencing efforts by Venter et al. suggested that the total number of human protein-coding genes might be less than 30,000 . This was a significant reduction from earlier estimates and suggested a closer similarity to the gene count of simpler organisms like the nematode Caenorhabditis elegans.
Comparative Genomics and Refined Estimates
Comparative genomics has played a crucial role in refining gene estimates. For instance, using the genome of the pufferfish Tetraodon nigroviridis, researchers estimated the human genome to contain between 28,000 and 34,000 genes . This method leverages the compact genome of the pufferfish to identify conserved sequences, providing a more accurate count.
Current Consensus on Gene Count
The most recent and widely accepted estimates place the number of human protein-coding genes at around 20,000 to 25,000. For example, a comprehensive analysis of the human genome sequence identified 26,588 protein-encoding transcripts with strong evidence, and an additional ~12,000 computationally derived genes with weaker supporting evidence . Another study suggested that the number of protein-coding genes might be as low as 20,500 after excluding non-conserved open reading frames (ORFs) .
Conclusion
The number of genes in the human genome has been a subject of extensive research and debate. Early estimates ranged widely, but with advancements in genome sequencing and comparative genomics, the current consensus suggests that the human genome contains approximately 20,000 to 25,000 protein-coding genes. This refined estimate has significant implications for our understanding of human biology and the complexity of the genome.
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