Scientific jargon can make even the most exciting topics seem boring or diffi­cult. This is especially true when it comes to DNA sequencing — readers have probably heard a bit about this topic but most have probably avoided reading articles on this topic due to all the scientific jargon.

Other Christians have ignored this topic because what they have read about DNA sequencing is almost always riddled with evolutionary assumptions. For exam­ple, in studies on the specific information content of human cells, scientists have compared human genetic information with that in mice, round worms, fruit flies, chimpanzees and even plants. This is fine if the scientists' objective is to figure out what the function of each gene is. However, the objective is too often to figure out "evo­lutionary lines of descent" or how the hu­man code came to evolve over time from very different ancestral organisms.

In spite of these regrettable evolution­ary speculations many of the results from these studies are of great interest. And the details are not too difficult once the jargon has been "de-coded."

22+1 Human Chromosomes⤒🔗

A chromosome is an extremely long string of chemical code — it is a strand of DNA which represents genetic information. When the string is wound up the whole thing assumes a heavier helical formation which, under certain circumstances, makes the very long string look relatively short and fat.

There are 22 different chromosomes which can be found in the nucleus of every human cell. These differ from each other in length and in light and dark markings. In pictorial representations of these chro­mosomes, scientists usually arrange them from longest to shortest, and they number them accordingly. There are also two chro­mosomes involved in gender determina­tion: the large X chromosome and the small Y chromosome. Each chromosome exhibits altogether different characteristics from the others. They carry different information in different arrangements and amounts.

Recently scientists finished the study of detailed information on each human chromosome. The whole effort, begun in the 1980s, ended when the analysis of hu­man chromosome number 1 was published on May 18/06. Since each chromosome is so different, allow me then to introduce you to some of your own chromosomes.

Chromosome 1←⤒🔗

Chromosome number 1, since it is the longest, not too surprisingly also repre­sents the largest amount of information. It controls more than 3100 packets of infor­mation which affect specific body charac­teristics. Each packet of information, or gene, typically calls for the synthesis of a single protein. Though it is an over-simpli­fication, the basic scientific understanding is that each individual's physical charac­teristics are determined by their genes.

Not only is chromosome number 1 very long, but it is also gene dense. Of all the chemical information present on hu­man chromosomes, scientists have only been able to find genes (protein coding in­formation) on 1-2% of the entire length of DNA. Some chromosomes contain more packed genetic information than others. The average for the whole human genome (all the chromosomes considered together) is 7.8 genes per million units of information (a unit is like an individual letter in a word). Thus in a million letters, on aver­age, there is coding for only 7.8 proteins. Chromosome 1 however, is more gene dense than this, with 14.2 genes on average per million units of information. These units are called nitrogen bases, or bases, or nucleotides. The way scientists represent this is 14.2  genes/Mb.

Scientists have no idea why there are such vast stretches of DNA in the human genome which do not code for proteins. Other kinds of organisms lack this feature. Scientists used to designate this non-cod­ing DNA as nonsense or junk DNA. They are not so ready to do that anymore. They now suspect that some of this information may be involved in signaling between cells, or various other regulatory activities. The "junk" label came from evolutionary theory which suggested that some features of the genome are left over from previous evolu­tionary uses but are no longer needed.

From a design point of view, we expect everything to be present for a reason.

Chromosome 1 is actually the third most gene dense chromosome, while the most gene dense is found way down the list at chromosome 19. With a gene density of 26.2 genes/Mb, chromosome 19 contains about 1500 genes although it is a very short structure. The second most gene dense chromosome is number 17, also way down the size range. With 16.2 genes/Mb, it con­tains 1266 genes. Amusingly, the most gene poor chromosome is chromosome 18, in size just between numbers 17 and 19. Chro­mosome 18 has 4.4 genes/Mb and only 337 genes. Even at first sight, it is apparent that each chromosome is entirely different in character from the others.

Chromosome 3←⤒🔗

Chromosome 3 is gene poor with a density of 8.8 genes/Mb. However the se­quences or order of letters or bases which make up each gene are actually quite long, so the gene coding part of the strand ex­tends to 49% of the strand.

This chromosome is interesting in that it has a large cluster of genes involved in the immune system. These genes call for the release of certain soluble proteins from cells in response to injury or an encounter with a foreign protein or an invading mi­crobe. These released chemicals, called chemokines, specifically attract a certain type of white blood cell called leukocytes. In response, these white blood cells will mi­grate to the source of the problem in order to deal with the invader. Among these sol­uble proteins are interferons, some of which are also produced from a gene cluster on chromosome 9.

Chromosome 11←⤒🔗

Chromosome 11 is one of the most gene rich chromosomes. It contains the fourth highest number of genes after chro­mosomes 1, 2 and 19. An important claim to fame of this chromosome is the large number of genes which contribute to our sense of smell. This sense involves hun­dreds of different kinds of sensor in the nose. Each type of sensor responds only to a single type of chemical or part of a large molecule. Our sense of smell is the blended perception of many different chemicals per­ceived at the same time. Each sensor type is controlled by an individual gene. Of the 856 olfactory (smell) receptor genes in the human genome, more than 40% of them are located on this chromosome. Some of these genes occur singly, but most are clus­tered together. The largest cluster contains 97 genes in sequence spread out over 1.5 ni­trogen bases.

Chromosome 11 also includes the gene for hemoglobin, one of the best stud­ied proteins. This was the first protein to be studied in its crystal structure, which gives an indication of the shape of the molecule. A mutant of this gene causes sickle cell anemia. Only three million ni­trogen bases away lies the gene which controls the formation of insulin, the first protein with its gene fully sequenced for nitrogen base order.

Chromosome 15←⤒🔗

Chromosome 15 is one of seven hu­man chromosomes with large sections pre­sent in duplicate sequences. For example, there are 37 nearly full-length copies of a certain sequence on this chromosome. No­body knows why they are there. There are also two copies on the Y — the male deter­mining — chromosome, and one each on chromosomes 2 and 10. Moreover almost 700 genes have also been identified on this chromosome.

Chromosome 16←⤒🔗

Chromosome 16 is also of interest. The US Department of Energy (DOE) began the process of sequencing this chromosome way back in 1988. Their interest lay in es­tablishing a base line for the normal condi­tion of this chromosome so that they could study the effects of radiation on human genetic material! This particular chromo­some was chosen because of the location there of the DNA repair gene ERCC4. Fur­ther interest also came from a cluster of genes on this chromosome which is in­volved in the transport within the body of toxic heavy metals. Toxic products were another biological interest of the DOE.

Chromosome 18←⤒🔗

Chromosome 18 has the lowest gene density of any human chromosome. One of the interesting features of this chromo­some are 24 gene deserts. A gene desert is a length of DNA 500,000 nitrogen bases long or longer, which contains no protein coding information. On this chromosome, 28 million nitrogen bases or 38% of the to­tal chromosome length are considered deserts. The sparsest region contains only 3 genes in 4.5 million nitrogen bases.

Probably because the genes are so scarce here, they are easier to study. One remarkable feature, also noted on chromo­somes 1 and 11, is the overlapping of genes. This means that part of the coding se­quence for one gene also forms part of the coding sequence for an adjacent gene. This discovery demonstrated that genes are not discrete units, but blocks of information which can in fact overlap. Scientists dis­covered 59 pairs of overlapping genes on this chromosome.

Another strange phenomenon, very apparent on this chromosome as well as on others, is alternative splicing of genes. Within the past few years, scientists have discovered that genes are not discrete blocks of information on the DNA strand. A lengthy block of DNA code is indeed copied into a molecule called RNA. The process is not, however, finished at this stage. Along come special enzymes which snip out large chunks of this information. The removed chunks are called introns. Other enzymes reattach the remaining sec­tions (called exons). On chromosome 18, there are typically many exons which must be glued together to form the practical in­formation unit or transcript (formerly called the gene). Appropriate enzymes glue together the exons in various different or­ders. Some exons may come from stretches of DNA far away from others to which they are later attached.

The opportunities for variation are readily apparent. Suppose there are exons ABCDEF waiting to be glued together. On one occasion perhaps only ACE are glued together, on another CEA, or BCDE etc etc. The capacity for the cell to synthesize dif­ferent proteins from the same block of information is stupendous. This phenomenon represents highly compressed information. Considering how every protein must be ex­tremely precisely produced, this storage and retrieval system is indeed an impres­sive mark of design. The numerous diseases so sadly associated with each chromosome, generally result from a small mistake in a specific protein's shape. Most of the time however, all the proteins are just right and the individual is healthy.

X/Y chromosome←⤒🔗

Of the 22 different chromosomes found in each person's cells, one set is in­herited from the mother and another set is inherited from the father. There are also two other chromosomes, the gender deter­mining chromosomes. Every person re­ceives an X chromosome from the mother. The father can contribute either an X chro­mosome (resulting in a girl) or a Y chro­mosome (resulting in a boy). Thus females have 22 pairs of chromosomes plus two Xs. Males have 22 pairs of chromosomes plus one X and a Y. These last two chromosomes are very remarkable indeed.

The X chromosome exhibits low gene density (7.1 genes/Mb) but since it is long, there are comparatively speaking, a lot of genes. Almost 1100 genes have been counted on the X chromosome. Of these, 99 genes code for proteins in the male sex organ. In addition, a large number of genes code for characteristics, which when the proteins are defective, show up mainly in males (sex linked conditions). Since females have two X chromosomes, generally they have a normal form of the gene on one of the two X chromosomes. For example, males are often red green color blind, while females, with one copy of the defective gene, are merely carriers. Such females have normal color vision but they can pass the colorblind characteris­tic along to their sons. Hemophilia is an example of a sex-linked disease and there are many others.

Since the X chromosome is very large compared to the Y chromosome, scientists have long wondered how females manage with so much extra genetic information. Generally extra chromosomal material has a conspicuous or even lethal effect. For ex­ample, when there are three copies of the very small chromosome 21 instead of two copies, Down syndrome results. In the case of the X chromosome, it appears that early in development, a young female randomly inactivates one or other of the X chromo­somes in each cell. Thus some cells ex­press the maternal X chromosome while others express the paternal copy. Not all genes on the X chromosomes are inacti­vated however.

The Y chromosome, though small, is most remarkable. Along this chromo­some, 12 genes have been discovered which control non-sexual characteristics. There are also 11 genes which are expressed mainly in the male sex organ. Most of these latter genes are located in a unique section of the chromosome. Here, there are lengthy sections of DNA coding which take the form of repeating se­quences. These can be either straight re­peats (for example abcdabcd), mirror images of each other (adammada) or sec­tions which can be read from either end with exactly the same order of letters (madamImadam). The latter is called a palindrome. These are very hard to design, yet on the Y chromosome there are 8 mas­sive palindromes, at least six of which contain genes. The palindromes are typi­cally about one million nitrogen bases long. One really spectacular one is 2.9 mil­lion nitrogen bases long with 2 smaller palindromes nested within it. Altogether 5.7 million nitrogen bases are involved in palindromes. These structures, are not merely interesting, they actually have a use in helping the cell maintain the accu­racy of the copied information. Indeed the accuracy of these sequences is 99.97%. One arm of a palindrome acts as a stan­dard or template that the other half can be corrected to match.

What amazing sophistication we see within every human cell. The details are so exquisite, so awesome that we cannot fail to give praise to our Lord, the Creator of all things. Many questions about the genome still abound, probably more than ever be­fore. However we know that further discoveries will be even more wonderful.