A person\'s genome is the sum of all the genes they possess. For many years, sci

Question

A person's genome is the sum of all the genes they possess. For many years, scientists estimated the number of human genes to be around 100,000. In the summer of 2000, scientists completed sequencing the 3.2-gigabase human genome. Researchers were surprised to find that humans only contain 25,000 genes. This represents about twice the number of genes in a fruit fly. Scientists also discovered that the majority of the human genome is repetitive DNA that does not code. What scientific and social implications does human genome mapping have for you? What purpose do you think this repetitive DNA serves?

Explanation / Answer

The DNA of eukaryotes contains “introns,” which protect the gene from damage. During transcription, these introns also get transcribed, and the pre mRNA contains introns. These introns are cut to form the mature mRNA, and the “exons” are spliced together. If the introns are not cut, the mRNA may code for non-functional proteins.

The results of human genome project are explained by the concept of alternative splicing. Alternative splicing, i.e. removal of different portions of genes of introns help in the synthesis of various proteins from the same mRNA. Thus, RNA splicing does not always result in the removal of same introns, which is an advantageous evolutionary strategy offered to organisms (they can make many new proteins). Thus, each genome codes for more than one protein, it may be three, four or more than that.

The repetitive DNA varies from one organism to the other, which serves the purpose of diversity and they indicate the DNA what we inherited from the ancestor species. The three-dimensional folding of the genome is also supported by the repetitive DNA.

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