DNA sequence analysis and structure

¶ … human DNA sequence composed of a series of letters such as 'accagacagt' and the objective was to decipher this jumble of letters and interpret the results. I suppose I should report that the process went smoothly and that after a bit of research I now consider myself an expert in regard to the new science of DNA Sequencing. However, I have a thousand more questions now than before I began and even the answers I came up with may or may not be correct. I do know for a fact that this is a pretty new art or science and its potential seems limitless. "DNA itself has thus far shown only modest evidence of possessing any intrinsic catalytic activities, although the prospect that more will be discovered in the future is surely plausible." (Cantor & Smith, 1999, xv)

The internet has made so many sites and processes available to the average person that home DNA testing may actually be a reality in the near future. But, this plethora of information is actually a bit overwhelming and therefore confusing. Results obtained on one site may not necessarily agree with the results of another site which obviously leads amateur Genomics practitioners such as my self to begin to doubt returned results and thus require professional confirmation. The key is that DNA Sequencing and interpretation will alter mankind's ability to identify 'medicine less' cures and maybe even lead to the creation of completely altered super humans. "Initiation of DNA replication holds the clue to what controls cell division and hence growth and differentiation." (Adams, 1991)

DNA

DNA is basically a two-stranded molecule and each strand is a polynucleotide composed of A (adenosine), T (thymidine), C (cytidine), and G (guanosine) residues. These residues are polymerized by "dehydration" synthesis in specific linear chain sequences. Scientists have clearly identified that the nucleotide residue are complementary along a double-stranded DNA molecule. For example, A forms two hydrogen-bonds with T. Or C. forms three hydrogen bonds with G. Therefore, in the majority of situations, a two-stranded anti-parallel complementary DNA molecule is said to fold to create a helical structure similar to a spiral staircase. Because of this, DNA is often referred to as a "Double Helix."

The true significance of a strand of DNA is that it truly holds the necessary information that is the blueprint or code for various genes. Consider that in the majority of organisms, genetics is established by breeding of pairs of parents and the results are the off-spring who would be a combination of the genetic codes of the two parents. "Despite the power of molecular biology to examine the information coded for by DNA, we have to know where in the DNA to look to find information of relevance to particular phenomena." (Cantor & Smith, 1999)

DNA and the internet

It has become relatively easy to find information pertaining to genes and the DNA sequence on the internet. There are sites where you simply add the sequence and hit submit and back come your results. The problem is that the results may include thousands of possibilities including other mammals such as mice, fungi and all types of other organism's DNA data feedback.

The results for this particular sequence came from the University of Stanford's eBlock web site and it offered many results but theses results seemed more consistent than some of the other sites I tried such as NCBI.gov. "Databases of eMOTIF and eMATRIX have been generated from eBLOCKs using eMOTIF-maker and eMATRIX -maker respectively. These two databases are available for search. To search a sequence against eBLOCKs, please enter your protein sequence in FASTA format and choose either eMOTIF or eMATRIX as your Search Method." (Stanford.edu, 2005)

DNA Sequence

The results of the internet search for this specific DNA sequence came back with a great deal of information which then required additional research. The results identified a serine protease better known as enterokinase or PRSS7. Enterokinase is an intestinal enzyme that helps the body initiate activation of pancreatic proteolytic proenzymes. "Enterokinase is a serine protease of the duodenal brush border membrane that cleaves trypsinogen and produces active trypsin, thereby leading to the activation of many pancreatic digestive enzymes. Overlapping cDNA clones that encode the complete human enterokinase amino acid sequence were isolated from a human intestine cDNA library." (Kitamoto et al., 1995) Dr. Kitamoto also points out that these structural features are conserved among human, bovine, and porcine enterokinase and that they can be detected only in small intestine.

Chromosome 21 has been identified as the smallest human autosome. "The enterokinase gene was localized to human chromosome 21q21 by fluorescence in situ hybridization." (Kitamoto et al., 1995) Researchers have concluded that Human chromosome 21 is of great importance to the medical research community because there are such a large number of genetic or familial disorders that can be mapped to this chromosome. Although many of these do not pertain directly to the enterokinase gene, chromosome 21 in general have been tied to Down syndrome, five percent of familial amyotrophic lateral sclerosis or motor neuron disease) and even Alzheimer's disease. The chromosomal translocations have also been tied to cancers like Ewing's sarcoma and acute myeloid leukemia.

This serine protease is a part of the intestinal brush border in the small intestine. "Congenital enteropeptidase deficiency is a rare recessively inherited disorder leading, in affected infants, to severe failure to thrive. The genomic structure of the proenteropeptidase gene (25 exons, total gene size 88 kb) was characterized in order to perform DNA sequencing in three clinically and biochemically proved patients with congenital enteropeptidase deficiency who were from two families." (Holzinger et al., 2002) Dr. Holzinger noted that defective alleles provided first evidence that proenteropeptidase-gene mutations are the primary cause of congenital enteropeptidase deficiency.