During an interview Richard Dawkins was asked if he could give an example of a mutation or evolutionary process that resulted in an increase of the information in the genome. The video of this interview shows he appeared to be stumped by this question. tinyurl.com/6f7zv5 . 
    Creationists leaped on this as evidence that such processes do not exist. I responded (URL above) that gene duplication is the process Dawkins was searching his memory for. In 1970, Dr. Susumu Ohno, a colleague of mine at the City of Hope Medical Center wrote a classic book entitled “Evolution by Gene Duplication.”  He showed the new genetic material and new information is added to the genome by the duplication of single genes, duplication of whole chromosomes and the duplication of whole genomes by polyploidy.
    Single gene duplication can occur during meiosis, the process that produces eggs and sperm in the gonads. During meiosis the chromosomes from the mother and from the father pair up. If individual genes or groups of genes line up end to end instead of next to each other, and if crossing over occurs between the genes, one of the gene or genes will be duplicated. This is called “unequal crossing over.” Over subsequent generations these duplicated segments can undergo changes by random mutation. One of the duplicated genes can serve its original function while the other can slowly change to adopt new functions in the cell.
    After human and other genomes were sequenced, it became apparent that gene duplication was a very common process. A classical example was the HOX genes, involved in the development of body form. In fruit flies (Drosophila) there is a single group of eight duplicate HOX genes. In mammals there are four such sections with nine to eleven duplicate HOX genes. The globin (of hemoglobin) genes are another example consisting of duplicate alpha, beta, delta, gamma and epsilon globin genes. There are hundreds of other examples.
    It was Ohno’s suggestion that whole genomes were duplicated at least once during the evolution from invertebrates to mammals that garnered the most excitement and attention. The examination of large databases of gene sequences in many vertebrate gene families has shown that both early whole genome duplication (about 350 to 650 million years ago) and widespread duplication of single or multiple genes occurred during vertebrate evolution (1, 2). These studies suggest at least one round of polyploidy as originally suggested by Ohno.
    Sequence studies have also shown that the rate of gene duplication is quite high, occurring one in one hundred times per gene per million years. If we assume the presence of 25,000 genes in the human genome, this represents 250 gene duplication events per one million years. Over a period of 400 million years this would be a billion gene duplications. With this degree of duplication it is not surprising that the vast majority of these duplicate genes are silenced within a few millions years (3). However, many are not and these form the major source of new information in the genome. To keep the size of the genome from exploding by so much gene duplication, the same unequal crossing process that produced the duplications can delete genes.
    Polyploidy is even more common in plants than in animals. Seventy percent of plant species were produced by polyploidy.
    One of the exciting new developments in genetics is the appreciation of the presence of “copy number polymorphisms” or CNPs (4). This refers to ways in which individuals differ on the basis of different numbers of duplicated genes. Some of these CNPs have been shown to be associated with different diseases.
    Dawkins seeming to be stumped obviously came from a lapse of memory rather than a lapse of knowledge. In his book, The Blind Watch Maker, on page 172 he says” “One of the main things that must have happened in the early evolution of living organisms was an increase in the numbers of genes… Bacteria have far fewer genes than animals and plants. The increase may have come about through various kinds of gene duplication.”
    In summary, despite their glee and widespread distribution of the Dawkins stumped interview, their celebration is short lived. The addition of new information to the genome has occurred at a massive scale throughout evolution.


1. McLysaght, A. et al: Extensive duplication during early chordate evolution. Nature Genetics 31: 200-204, 2002.

2. Gu, X. et al. Age distribution of human gene families shows significant roles of both large- and small-scale duplication in vertebrate evolution. Nature Genetics 31:205-209, 2002.
    
3. Lynch, M and Conery, J.S.: The evolutionary fate and consequences of duplicate genes. Science 290:1151-1155, 2000.

4. Redon, R. et al: Global variation in copy number in the human genome. Nature 444:444-454, 2006.