convention holds that humans and chimpanzees we differ very little in our DNA. However, there are new evidence to suggest that the differences could be much more drastic . The mutations that cause insertions and deletions in DNA are those that produce the genetic difference between the two species, but they are not normally included in estimates of diversity.
also there are areas with large similarities that are often affected by selective restrictions. Every time there are more functions to the so-called "junk DNA" which indicates that the similarities in this type of DNA are not necessarily the result of common ancestry.
Future research will help to understand this information so important in the debate about origins.
Creationists have long maintained that the similarities between the DNA of man and chimpanzee are not as many as believed. A new study published in the Proceedings of the National Academy of Sciences (PNAS) could help confirm this.
There is a widespread view according to which
"the common chimpanzee (Pan troglodytes) is our closest relative. Its gene sequence is almost identical (98.8%) to ours, and almost 6 million years shared a common ancestor. " 1
The assumption that humans split from chimpanzees so long also forms the basis for the mitochondrial clock, 2
" which continues to be widely used for 'dating' of human evolution and population movements, ancient and modern. " 3
In the popular book, Genome (Genome) , Matt Ridley says
"A part of the merger of chromosomes 2, the visible differences between chromosomes of chimpanzees and humans are few and small: in thirteen chromosomes there is any difference. If you select at random any "paragraph" in the human genome, found that few "letters" are different: an average of less than two percent. We are approximately ninety-eight percent of chimpanzees, and they are in a limit insurance trust, ninety-eight percent of human beings. If this does not sink your self-esteem, think that chimpanzees are only ninety-seven percent gorillas in the same way humans are ninety-seven percent gorillas. In other words, we become more like chimpanzees than chimpanzees to gorillas. "
A creationist response to these arguments concerning the similarities between humans and chimpanzees is that
" DNA of chimpanzees is far from fully encoded so that a comparison can be made effective. " 5
addition, such testing can also be explained (indeed, predict) easily by using the concept of a common designer:
"Since the DNA encoding the structures and biochemical molecules, we should expect similar creatures DNA had a more similar. Monkeys and humans are mammals, with similar forms, therefore, both have similar DNA. We should expect that humans have more similarities with other mammals, such as pork, rather than a reptile, as the rattlesnake. And it is. Humans are very different from yeast, but have some biochemical common. Therefore, we expect that human DNA is more than the DNA of the yeast DNA of the monkey. " 6
In a recent article, 7 David A. DeWitt, commented on an investigation which found that both species are only 95% identical-by considering insertions and deletions, " 8 showing that the estimate of the differences depend mainly on the type of DNA that is compared. Reference is made to differences between humans and chimpanzees that are difficult to quantify when assessing the sequence divergence (ie, differences between the bases of humans and chimpanzees).
Some of these differences include shorter telomeres in humans, one chimpanzee genome 10% larger, and large differences in chromosomes 4, 9, 12 and Y chromosome, to name a few. Indeed, estimates of the similarities
"does not adequately represent the subtle changes in genome organization." 9
consider 
do the gaps in the DNA
Previous estimates of the divergence of the sequences were exclusively focused on the substitutions of DNA bases, ie a base (or "letter" of DNA: A, T, C or G) is replaced by another. The new estimate, which gives a much lower sequence similarity, also considers insertions and deletions, called indels, (which occur when a base is added or subtracted, often resulting in what is known as a frameshift mutation or frameshift gap ), apart from the substitutions of the bases. The author of this research, Roy J. Britten said:
"I consider it appropriate to take into account the total distances of the gaps in estimating the interspecies divergence. In fact, these DNA strands are absent in a genome and present in another. In the past, indels have often told regardless of its length, and have been added to the calculation of base substitutions, as this is convenient for phylogenetics. " 8
Their findings give support to the idea that much of the failure of hybridization between the DNA of chimpanzees and humans is the result of DNA loss as a result of indels. Later, Britten Contributed to a review paper which confirmed the initial results. In fact, they found that
"the 5% difference, already published, will surely be an underestimate, possibly more than a factor of 2." 10
recently Anzai et al . published a report in the A tsp of the National Academy of Sciences (PNAS) confirms this statement. In this study, we sequenced about half of the region of the MHC (major histocompatibility complex),
"which to date represents the longest continuous sequence in the species [chimpanzees], our closest evolutionary relative. "
This region has been described as part of our genome that" rapidly evolving. " Although it has been argued that the similarity between human and chimpanzee in the MHC is
"so great that the alleles had to arise before the alleged divergence between human and chimpanzee,"
the results of the sequence actually reduced the estimates up to 86.7%. In fact, the real difference between the two species (taking into account indels) is more than 5%, more than a factor of 2. Not only that,
"evolutionists now recognize that the genetic basis of MHC complexes can originate independently";
is, at least some similarities, they can not be attributed to a descent common.
The human genome contains two Class I MHC genes, MICA and MICB, but I lel chimpanzees contains only one gene in this place, the Patr-MIC. According to evolutionary speculation, about 33-44 million years ago a 95-kilobase deletion between two human genes formed the hybrid gene of the chimpanzee, the divergence preceding a long established community of 6 million years. Since the two ends of the chimpanzee gene appear to coincide with the beginning of MICA and MICB end of the human, it may seem logical possibility of a common ancestry. However, even some humans contain a single gene in this region (HLA-B * 4801), very similar to that found in chimpanzees.
The study notes that
"is quite intriguing that a deletion of the same size as regards the same genes and region (MICA / B) occurred at different times in different species of primates. " 12
Still alleges that similar changes in DNA structure can not be attributed to convergence, but due to common ancestry! It is clear that, "failures" like can arise independently in different species (discussed in detail by Woodmorappe 13). The hypothesis that a designer would have created the same structures for the same functions seems a more logical explanation of these data. As stated Woodmorappe , 11 for prevent the similarities of the MHC of different primates were mixed over alleged millions of years, should have been a strong selective pressures, which would further weaken the prospects for the future of evolution.
research Anzai et al. also mentions a few differences between humans and chimpanzees may be the result of genetic changes in MHC genes, including the difference in the handling of infectious agents, such as AIDS, hepatitis B and C, and susceptibility to Plasmodium falciparum . Therefore, the differences observed in these genes can more accurately represent the "true" divergence between the two species than previous estimates.
Although these results are interesting, there has been debate about whether indels should be included in the estimates of divergent sequences. For example, a mutation called translocation can make a separate DNA segment of a chromosome and inserted into another. The original research Britten briefly discussed these events and found to be frequent. Since indels were defined as the total length of separation "in the genomes, estimates not be able to reflect this type of mutations easily. 14 hope for future research to help understand the changes in genome organization and give us clues about how these changes can be included in the estimates of the similarities between human and chimpanzee
The difference between coding and noncoding DNA
Other studies have given estimates in excess of 98.6%. For example, Wildman et al. 15 compared about 90 kilobases of human DNA to the chimpanzee, and found a similarity of 98.86%, including indels. This is an important test, considering that is directly opposed to the data presented by Britten and Anzai et al. However keep in mind that these estimates using different types of DNA. Wildman team examined DNA encoding only a few genes. Here, the changes do not like (those that affect the protein structure encoded by changing the specific amino acid) are subject to purifying selection. This means they can be selected against if they have any effect on protein function.
Similarly, a study of chromosome 21 (the smallest chromosome in the human genome) found only 3.003 nucleotide differences in more than 400 kilobases. It was shown that "differences in coding, promoter, and the regions of junction of exons and introns were 0.51 ± 0.02%, 0.88 ± 0.03% and 0.85 ± 0.02%, respectively, much lower than presented earlier estimate of 1.23% in genomic regions, 16 with a total of 99.3% similar. Within an evolutionary framework these results confirm that chimpanzees are our closest relatives. However, this finding appears contradict the certainty that there is a high substitution rate on chromosome 21, leading to the conclusion
"... the level of similarity observed in transcribing units in this research is attributed to presence of purifying natural selection used in the most important functional parts of genes, including promoters, coding regions and intronic regions near the exon-intron border. " 16
It Thus, estimates with high similarity index refer particularly to regions of DNA coding that are functionally limited. Research by Britten et al. and Anzai et al. take into account the non-coding DNA, which may be less constrained and therefore more free to accumulate random mutations. Thus, this noncoding DNA serves as a more accurate representation of the true divergence. Naturally, it is reasonable in the context of biblical creation, there is much similarity where the functions of proteins is vital, since the same proteins would be used for a common designer, for the same structures. 6 The logical consequence is that non-coding DNA, being more restricted, probably contains more differences.
Returning to the investigation of Anzai et al. , in which it was discovered that chimpanzees and humans have a 86.7% similarity, see a general trend of greater similarity in coding regions. While
"most non-MHC genes are related to basic cellular functions (homeostatic) that require both interindividual homogeneity as interespecial"
MHC genes
"have to adapt to the microbiological habitat of every species. "
Therefore, purifying selection tends to maintain the structural conservation of other genes as a result of their specific functions. We conclude that an estimate of 86.7%
"may be a more accurate representation of the similarity between the total genome sequences of humans and chimpanzees,"
that previous estimates of 98.6%. Since
"the biggest difference between the sequences of humans and chimpanzees is well attributable to indels, " 12
estimates do not include these mutations ignore a large source of potential differences. Recently, research has found that indels are a major source of variation between humans and chimpanzees. 8, 10, 12 should also be noted that, in contrast with the examples of very similar sequence, sequence divergence in some regions can exceed 20%. 8 As noted De Witt, estimates can be
"misleading because it depends on what you compare. " 7
junk DNA
Introns are regions of DNA in the genome that do not encode a product protein, and therefore assumed to have no function. A consequence of this,
"introns of a specific gene are often compared with those of other organisms where there are differences of base pairs between the sequences, these differences are considered as an indication of degree and time of divergence from the point in which shared a common ancestor. " 17
Indeed, in a creationist context, functional introns should not be very different in humans and chimpanzees, even nonexistent, but the evidence stacked in favor of the introns are not, after all, devoid of function. And the assumption that if it were,
"could end up being a typical story about how Orthodoxy can derail an objective analysis of the facts." 18
Other junk-DNA forms of which clearly stated that lacked function and therefore able to mutate at random, in fact contradict the evolutionary phylogeny, such as pseudogenes, which are common to humans and gorillas, but absent in chimpanzees. The CYP pseudogene present only in chimpanzees, and a substitution in the pseudogene Alpha-1, 3GT that appears in cows, squirrels, monkeys and gorillas. Many common substitutions occur in a non-random, it also weakens the strength of the hypothesis of common ancestry. 13 have published numerous articles explaining the functions of alleged forms of "junk" 13, 17, 19-22 and publications is encouraging to see that evolutionists are waking up and recognizing this fact as important. The preservation of introns
"... suggest doing something indispensable. And really a lot are transcribed into varieties of RNA that play a larger range of functions than biologists imagined. Some scientists now suspect that much of what makes a person "and a species-different from the other, are the variations in the gems that are hidden in our DNA" junk. " 23
Therefore, the similarities of introns fit quite well with the creationist paradigm.
DNA is not everything
I suggest that more rigorous research is needed to review these tests will also find research that inherent differences within the species of chimpanzee. Indels can be clearly seen as the intrinsic differences between species. The DNA sequence is not all that distinguishes the different types of organisms. As Steve Jones said in an appointment Creation:
"We also have 50% of Pooled DNA with bananas, but that does not make us bananas, or from the waist up or waist down. " 24
There is evidence to clearly demonstrate that the" DNA is not everything " eg, mitochondria, ribosomes, the endoplasmic reticulum, and cytosol are transmitted from father to son unchanged (except for possible mutations in the mtDNA). In fact, the gene expression is under the control of the cell. 25
Some animals have undergone huge genetic changes, yet their phenotypes have remained virtually identical. 26 These epigenetic marks
"can dramatically affect the health and characteristics of an organism, some even passed from parents to children," yet these brands do not change the underlying DNA sequence. " 27
These tests give great support to the reproduction of species (Genesis 1:24-25, 1 Corinthians 15:39), because the structures present in the parents are preserved in the offspring.
Conclusion
This is an exciting time to creationists when taking into account the indels, the estimates of the similarities between humans and chimpanzees continue to fall. It is clear that the two species are very similar DNA sequences (many identical structures are present in both, so this was also expected from a creationist model), previous estimates of 98.6% sequence identity may have suffered a huge blow. The investigations to come will surely shed light on the many differences between humans and other animals, and continue to affirm the truth of Genesis .
References 1. Cyranoski, D.: "Almost Human", Nature 418, (6901), 2002. p.910-912
2. Gibbons, A.: "Calibrating the Mitochondrial Clock", Science, 279 (5347), 1998. p.28-29.
3. Howell, N., Smejkal, CB, Mackey DA, Chinnery, PF, Turnbull, DM and Herrnstadt, C.: "The pedigree rate of sequence divergence in the human mitochondrial genome: there is a difference between phylogenetic and rhythm pedigree ", American J. Human Genetics 72, (3), 2003. p.659-670.
4. Ridley, M., Genome, HarperCollins Publishers, New York. p.28. 1999.
5. Batten, D.: "Similidud human and chimpanzee DNA: evidence for a relationship evulutiva? Creation 19, (1), 1997. p.21-22.
6. Sarfati, J., "Refuting Evolution 2", Creation Ministries International, Brisbane, Australia, 2002. p. 112-113
7. DeWitt, DA, "> 98% similarity between chimpanzee and man? Not anymore. " TJ 17, (1), 2003. p.8-10.
8. Britten, RJ: "The difference between DNA samples of chimpanzee and human DNA is 5%, counting indels. Proc. Nat Acad. Sci USA. 99, (21), 2002. p.13633-13635.
9. Hacia, JG: "The genome of the apes." Trends in Genetics, 17, (11), 2001. p. 637-645.
10. Britten, RJ, Rowen, L., Williams, J. and Cameron, RA: "Most of the differences between related DNA samples is due to indels. Proc. Nat Acad. Sci USA, 100, (8), 2003. p.4661-4665.
11. Woodmorappe, J.: "Noah's Ark: A feasibility study." Institute for Creation Research, El Cajon. p. 203, 1996.
12. Anzai, T., Shiina, T., Kimura, N., Yanagiya, K., Kohara, S., Shigenari, A., Yamagata, T., Kulski, JK, Naruse, TK, Fujimori, Y., Fukuzumi, Y., Yamazaki, M., Tashiro, H., Iawmoto, C. , Umehara, Y., Imanishi, T., Meyer, A., Ikeo, K., Gojobori, T., Bahram, S. and Inok, H.: Sequence comparison of class I MHC regions of humans and chimpanzees discovered that insertions / deletions are the major cause of genomic divergence. Proc. Nat Acad. Sci USA, 100, (13), 2003. p.7708-7713.
13. Woodmorappe, J.: "Are pseudogenes" errors communes "between the genomes of primates?" TJ, 14, (3), 2000. p.55-71.
14. Cartwright, RA: Personal communication, 8 July 2003.
15. Wildman, DE, Uddin, M., Liu, G., Grossman, LI and Goodman, M.: "Impact on natural selection are forming an identity of 99.4% of detached DNA between humans and chimpanzees, engendered the gender. "Homo. Proc. Nat Acad. Sci USA 100, (12), 2003. p.7181-7188.
16. Shi, J., Xi, H., Wang, Y., Zhang, C., Jiang, Z., Zhang, K., Shen, Y., Jin, L., Zhang, K., Yuan, W., Wang, Y., Lin, J., Hua, Q., Wang, F., Xu, S., Ren, S., Xu, S., Zhao, G., Chen, Z., Jin, L. and Huang, W., "The divergence of genes on human chromosome 21 and other hominids and substitution rate variation between units transcriber." Proc. Nat Acad. Sci USA 100, (14), 2003. p.8331-8336.
17. Walkup, LK: DNA garbage: waste of evolution or God's tools? "TJ, 14, (2), 2000. p.18-30.
18. Mattick JS, quoted in: Gibbs, WW: "The gene invisible: gems among the trash." Scientific American 289, (5), 2003. p.46-53.
19. Batten, D.. "More garbage reclaimed." TJ, 16, (2), 2002. p.8.
20. Woodmorappe, J.: "pseudogenética function: regulation of gene expression." TJ, 17, (1), 2003. p.47-52.
21. Woodmorappe, J.: "pseudogenetica function: more evidence." TJ, 17, (2), 2003. p.15-18.
22. Woodmorappe, J.: "junk DNA defendant." TJ, 18, (1), 2004. p.27-33.
23. Gibbs, WW: "The unseen genome: gems among the trash. Scientific American 289 (5), November 2003. p.46-53,
24. J. Jones, quoted in: Wieland, C., "Humanitas furry?" Creation 24 (3) :10-12, 2002.
25. Williams, AR: "Paradigms that jump." TJ, 17, (1), 2003. p.19-21.
26. Fox, D.: "Countries Wallaby." New Scientist, 175 (2354), 2002. p.32-35.
27. Gibbs, WW: "The unseen genome: beyond DNA." Scientific American 289, (6), 2003. p.106-113.
0 comments:
Post a Comment