Researchers say it was previously thought that much of the human genome was ‘junk DNA’, but it turns out it’s not that simple.
In the spring of 2003, scientists working on the Human Genome Project completed the sequence of the human genome, reports Science focus.
However, this human “Book of Life” remains difficult to read, even for the world’s leading geneticists. Researchers are still sifting through the data.
One of the biggest questions that has arisen is: why is the human genome so large?
The striking thing about the completed human genome was how little it seemed to do anything at all. The human genome contains approximately three billion nucleotide pairs. Of this amount, less than 2% (about 20,000) consists of genes that code for proteins that control the cells of our body. But what does the rest of the human genome do?
Some called this part junk DNA, because they considered it genetic gibberish – a leftover from millions of years of evolution. While some of this genetic “gibberish” really doesn’t work, it’s not all useless.
Gradually, scientists are beginning to shed light on this dark side of the human genome. Some of this ‘garbage heap’ performs crucial regulatory or modification functions for genomes that encode proteins. Some liken these DNA sequences to volume knobs that control the expression of our genes.
Large portions of the dark genome are also made up of long, repetitive DNA sequences known as transposons. They play an important role in the expression of genes related to crucial stages of human evolution. Scientists suggest they are related to our ability to adapt to the environment.
Transposons, also called “jumping genes,” can move from one region of the genome to another. This ability can cause significant genetic mutations and changes.
For example, transposons may be associated with the development of opposable thumbs in humans, as well as with the loss of the tail in us and other great apes.
In some cases, ‘jumping genes’ are associated with the development of tumors, as well as with some hereditary diseases. For example, hemophilia and Duchenne muscular dystrophy arise from repetitive DNA sequences associated with transposons.
In the coming decades, scientists hope to decipher this obscure human genome, leading to a new generation of treatments for genetic diseases.
