Skip to comments.Scientists Analyze Chromosomes 2 and 4: Discover Largest "Gene Deserts"
Posted on 04/13/2005 6:20:23 PM PDT by PatrickHenry
A detailed analysis of chromosomes 2 and 4 has detected the largest "gene deserts" known in the human genome and uncovered more evidence that human chromosome 2 arose from the fusion of two ancestral ape chromosomes, researchers supported by the National Human Genome Research Institute (NHGRI), part of the National Institutes of Health (NIH), reported today.
In a study published in the April 7 issue of the journal Nature, a multi-institution team, led by [load of names deleted, but available in the original article].
"This analysis is an impressive achievement that will deepen our understanding of the human genome and speed the discovery of genes related to human health and disease. In addition, these findings provide exciting new insights into the structure and evolution of mammalian genomes," said Francis S. Collins, M.D., Ph.D., director of NHGRI, which led the U.S. component of the Human Genome Project along with the DOE.
Chromosome 4 has long been of interest to the medical community because it holds the gene for Huntington's disease, polycystic kidney disease, a form of muscular dystrophy and a variety of other inherited disorders. Chromosome 2 is noteworthy for being the second largest human chromosome, trailing only chromosome 1 in size. It is also home to the gene with the longest known, protein-coding sequence - a 280,000 base pair gene that codes for a muscle protein, called titin, which is 33,000 amino acids long.
One of the central goals of the effort to analyze the human genome is the identification of all genes, which are generally defined as stretches of DNA that code for particular proteins. The new analysis confirmed the existence of 1,346 protein-coding genes on chromosome 2 and 796 protein-coding genes on chromosome 4.
As part of their examination of chromosome 4, the researchers found what are believed to be the largest "gene deserts" yet discovered in the human genome sequence. These regions of the genome are called gene deserts because they are devoid of any protein-coding genes. However, researchers suspect such regions are important to human biology because they have been conserved throughout the evolution of mammals and birds, and work is now underway to figure out their exact functions.
Humans have 23 pairs of chromosomes - one less pair than chimpanzees, gorillas, orangutans and other great apes. For more than two decades, researchers have thought human chromosome 2 was produced as the result of the fusion of two mid-sized ape chromosomes and a Seattle group located the fusion site in 2002.
In the latest analysis, researchers searched the chromosome's DNA sequence for the relics of the center (centromere) of the ape chromosome that was inactivated upon fusion with the other ape chromosome. They subsequently identified a 36,000 base pair stretch of DNA sequence that likely marks the precise location of the inactived centromere. That tract is characterized by a type of DNA duplication, known as alpha satellite repeats, that is a hallmark of centromeres. In addition, the tract is flanked by an unusual abundance of another type of DNA duplication, called a segmental duplication.
"These data raise the possibility of a new tool for studying genome evolution. We may be able to find other chromosomes that have disappeared over the course of time by searching other mammals' DNA for similar patterns of duplication," said Richard K. Wilson, Ph.D., director of the Washington University School of Medicine's Genome Sequencing Center and senior author of the study.
In another intriguing finding, the researchers identified a messenger RNA (mRNA) transcript from a gene on chromosome 2 that possibly may produce a protein unique to humans and chimps. Scientists have tentative evidence that the gene may be used to make a protein in the brain and the testes. The team also identified "hypervariable" regions in which genes contain variations that may lead to the production of altered proteins unique to humans. The functions of the altered proteins are not known, and researchers emphasized that their findings still require "cautious evaluation."
In October 2004, the International Human Genome Sequencing Consortium published its scientific description of the finished human genome sequence in Nature. Detailed annotations and analyses have already been published for chromosomes 5, 6, 7, 9, 10, 13, 14, 16, 19, 20, 21, 22, X and Y. Publications describing the remaining chromosomes are forthcoming.
The sequence of chromosomes 2 and 4, as well as the rest of the human genome sequence, can be accessed through the following public databases: GenBank (www.ncbi.nih.gov/Genbank) at NIH's National Center for Biotechnology Information (NCBI); the UCSC Genome Browser (www.genome.ucsc.edu) at the University of California at Santa Cruz; the Ensembl Genome Browser (www.ensembl.org) at the Wellcome Trust Sanger Institute and the EMBL-European Bioinformatics Institute; the DNA Data Bank of Japan (www.ddbj.nig.ac.jp); and EMBL-Bank (www.ebi.ac.uk/embl/index.html) at EMBL's Nucleotide Sequence Database. [Links in original article.]
NHGRI is one of the 27 institutes and centers at NIH, an agency of the Department of Health and Human Services. The NHGRI Division of Extramural Research supports grants for research and for training and career development at sites nationwide. Additional information about NHGRI can be found at www.genome.gov.
I do believe that their are hurdles to test faith. You have read Job haven't you?
Well, I know how to read better than I know how to type :P The bible is very clear that God created man in his image. If you think god is an ape you can believe that.
I call it Intelligent Design.
LOL! What a moronic statement. You believe in god thats a distraction that make keeps us from working of SS reform! WAH WAH! OMG!
It was a joke denoted with this ":P" :P HAR HAR
Very true. Evos don't have the scientific evidence available to the Creos who base everything on a book written by men.
Some people swear that the Bible is the Written word of God. Yet, when confronted by passages advocating slave ownership and beating they explain that the "times were different" then.
Hard to think of God as a moral relativist, but what do us Evos know.
Darwin was just the starting point. The genenome sequencing is going to trash the creationist unbelief.
Well, it's certainly a trove of evidence which supports evolution, but we've already accumulated mountains of evidence for the last 150 years, and although the science community is convinced of the theory's value, nothing has made the slightest impression on creationism. I suspect that will continue to be the situation.
Isn't it beautiful?
Only if they don't have brains.
Nope, it only allows the prediction of sequence. If you want to know the actual sequence, you still have to do it the tedious way.
Nope, it means that we evolved from a common ancestor.
The centromere is the little connecting structure that holds 2 matching chromosomes together (at least, until mitosis or meiosis occurs). When you see a picture of chromosomes that look like X's, the centromere is where the X's cross.
I, for one, am not confused. Neither are my colleagues, who practice a variety of faiths. The theory of evolution for us is just a tool, and has nothing to do with faith.
Correlation is a statistical term, and I do not recall using that word today in the context of evolution. Nor did I make a claim about correlation equaling causation, since I do not use the term for that purpose at all (and I do use the term frequently). I'm not even sure how the concept of correlation applies here. We talk about sequence homology--the mouse and rat gene xyz have 97% homology, while the human gene is only 93% homologous to that of mouse or rat, etc. Evolution can be traced by comparing the homology of genes across various species.
Biologists...riding in the short bus of science.
I stand corrected, but the prediction is usually pretty damn good, especially in bacteria (my area).