Gene Duplication

881 Words4 Pages
When the human genome sequence was released in 2003, it was discovered that it contains only 23,000 genes (Crollius et al., 2000 as cited in Chen, 2012). In comparison, the nematode C. elegans, a much simpler organism, has a similarly sized genome. This demonstrates that there is no real connection between gene number and organismal complexity. The concept of one gene leading to the formation of only one protein is no longer valid. Instead, a posttranscriptional process called alternative splicing (AS) exists in which various unique transcripts, or isoforms, can be produced from a single gene in eukaryote organisms. It involves removing introns from a strand of pre-mRNA, while splicing the remaining exons together to produce the mature…show more content…
In a close relative of vertebrates, Ciona, the TnI gene is only present as a single copy. However, Ciona creates three different isoforms for this gene through alternative splicing, each of which resembles one of the three copies of TnI in vertebrates in terms of functionality. This suggests that the evolution of the TnI gene to function in different muscle types originated from AS events that produced three functional transcripts from a single gene, providing a selective advantage to the relatives of vertebrates (Maclean et al., 1997 as cited in Chen, 2012). Furthermore, the alternative splicing of pre-mRNA strands of specific genes is critical for the well-being of certain organisms (Modrek et al., 2001).
The genes that are affected by alternative splicing in humans tend to produce molecules that are essential for the cell. The major class of these molecules is cell surface proteins and receptors, which are involved in cell surface interactions and signalling. Approximately 30% of alternatively spliced genes make molecules with functions pertaining to the immune system, such as immune cell surface receptors. The splicing of pre-mRNA strands can produce a variety of receptor and signal transduction molecules that enable cells to respond to foreign invaders. Alternative splicing ultimately helps humans better adapt to
Get Access