Theory of Intelligent Design, the best explanation of Origins

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Theory of Intelligent Design, the best explanation of Origins » Molecular biology of the cell » Development biology » Gene expression and regulation of cell differentiation

Gene expression and regulation of cell differentiation

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Gene expression and regulation of cell differentiation

http://reasonandscience.heavenforum.org/t1742-gene-expression-and-regulation-of-cell-differentiation

Its said that gene mutations provide macro evolutionary changes. But if a mutation occurs at one place in the genome, all it can do, is to change the development of a particular part. In order to have macro evolutionary changes, the whole body must develop into a specific new direction , and for example to change from scales to feathers, it needs completely new correct genomic information , and feathers that are not fully formed will not provide any survival advantage.  That means, the whole genetic code must differ, and slight changes must occur in the whole body. There would have to be simultaneous genetic mutations, and all provide change of a specific direction.  Each change would have to consist in a gradual change not only of a specific loci and  mutation, but the whole genetic code would have to change as well in order to move on and provide a change of the body as a whole. Why would we have not to expect to see much bigger variation of hybrid transitional forms half chimp, half human, for example ?

http://www.dnalc.org/view/16759-Concept-37-Master-genes-control-basic-body-plans-.html

The development of an organism — from a fertilized egg, through embryonic and juvenile stages, to adulthood — requires the coordinated expression of sets of genes at the proper times and in the proper places. Studies of several bizarre mutations in the fruitfly, Drosophila, provided keys to understanding the molecular basis of large-scale developmental plans. Early embryonic genes express proteins that set up the orientation and define the body segments of the fly embryo. Then "homeotic" genes act on the segments to make the body parts distinct to each segment. Sequence analysis showed that homeotic genes from Drosophila and vertebrate animals share a 180-nucleotide region, called the homeobox. These homeobox proteins have structures highly similar to the regions of regulatory proteins that bind to DNA promoters and enhancers. Thus, a homeotic protein elicits coordinated expression when the protein binds to a specific promoter or enhancer sequence shared by a number of genes involved in the development of body region or segment.


Christian Schwabe, the non-creationist sceptic of Darwinian evolution from the Medical University of South Carolina (Dept. of Biochemistry and Molecular Biology), wrote: (Mini Review: Schwabe, C., 1994. Theoretical limitations of molecular phylogenetics and the evolution of relaxins. Comp. Biochem. Physiol.107B:167–177).

‘Control genes like homeotic genes may be the target of mutations that would conceivably change phenotypes, but one must remember that, the more central one makes changes in a complex system, the more severe the peripheral consequences become. … Homeotic changes induced in Drosophila genes have led only to monstrosities, and most experimenters do not expect to see a bee arise from their Drosophila constructs.’

Research in the six years since Schwabe wrote this has only born out his statement. Changes to homeotic genes cause monstrosities (two heads, a leg where an eye should be, etc.); they do not change an amphibian into a reptile, for example. And the mutations do not add any information, they just cause existing information to be mis-directed to produce a fruit-fly leg on the fruit-fly head instead of on the correct body segment, for example.

The same as the blueprint of a designer is the genetic code  in a biological system, in case of humans encoded as DNA sequences within the 23 chromosome pairs in the cell nuclei. In the same way, as the overall blueprint of a car includes all different parts, like the engine, car chassis,  cockpit , wheels etc., the genetic code of the whole  body plan  contains many different organs such as the heart, liver, or lungs. While each car must be built up from scratch with outside intervention and information, through robots and humans, biological systems do all by their own, the whole mechanism of cell division ( mitosis ) and duplication into daughter cells is pre-programmed in the genome. All the informations and instructions , the blueprint for producing a new body is contained as well in each cell.

http://www.indiana.edu/~rcapub/v18n1/p4.html

The process of embryo development is something akin to a miracle: a single, fertilized cell develops into an organism with millions of specialized cells, all working together. The regulation of these developmental events is currently a major area of biological research, which seeks to understand the genetic and molecular controls that produce a complicated organism. The human body contains about 100 trillion cells ( 10^14),and is made of  about 200 different types of cells, and within these cells there are about 20 different types of structures or organelles.

Different cells have different jobs. Each cell has a size and shape that is suited to its job. Cells that do the same job combine together to form body tissue, such as muscle, skin, or bone tissue. Groups of different types of cells make up the organs in your body, such as your heart, liver, or lungs. Each organ has its own job to do, but all organs work together to maintain your body. A group of different organs working together to do a job makes up a system. All the systems in your body are like members of a team whose job it is to keep you alive and healthy. When i build a car, the build-up sequence plays a important role. First i need to make the individual parts, and in the end, the whole machine is built up together. In biological systems different cells are made through gene expression in the genome.


Christian Schwabe, the non-creationist sceptic of Darwinian evolution from the Medical University of South Carolina (Dept. of Biochemistry and Molecular Biology), wrote: (Mini Review: Schwabe, C., 1994. Theoretical limitations of molecular phylogenetics and the evolution of relaxins. Comp. Biochem. Physiol.107B:167–177).

‘Control genes like homeotic genes may be the target of mutations that would conceivably change phenotypes, but one must remember that, the more central one makes changes in a complex system, the more severe the peripheral consequences become. … Homeotic changes induced in Drosophila genes have led only to monstrosities, and most experimenters do not expect to see a bee arise from their Drosophila constructs.’

Research in the six years since Schwabe wrote this has only born out his statement. Changes to homeotic genes cause monstrosities (two heads, a leg where an eye should be, etc.); they do not change an amphibian into a reptile, for example. And the mutations do not add any information, they just cause existing information to be mis-directed to produce a fruit-fly leg on the fruit-fly head instead of on the correct body segment, for example.



http://www.nature.com/scitable/topicpage/gene-expression-regulates-cell-differentiation-931

All of the cells within a complex multicellular organism such as a human being contain the same DNA; however, the body of such an organism is clearly composed of many different types of cells. What, then, makes a liver cell different from a skin or muscle cell? The answer lies in the way each cell deploys its genome. In other words, the particular combination of genes that are turned on (expressed) or turned off (repressed) dictates cellular morphology (shape) and function. This process of gene expression is regulated by cues from both within and outside cells, and the interplay between these cues and the genome affects essentially all processes that occur during embryonic development and adult life.




Deformities in which people have misshapen limbs are a perfect example that mutations in genetics can result in a change of body layout. // well, the misshapen limbs are still the limbs. Its as the pistone of a car motor , for example. It might happen that during the manufacturing process, something goes wrong, and the piston happens to have some kind of deformity, and will not be functional. Thats quite a different thing, as to say, the wrong manufacturing process gives raise to the battery of a electric car. And many millions of years of manufacturing errors of the car pistone will give rise to a fully functioning battery for a electric car. And many other errors in the end permit a gasoline car transforming into a electric car. How irrational is that ?? but thats exactly your proposal.



Last edited by Admin on Tue Apr 28, 2015 6:12 am; edited 3 times in total

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http://www.ideacenter.org/contentmgr/showdetails.php/id/841

Some biologists have also envisioned special mutations in regulatory homeobox or "Hox" genes, where simple mutations might be able to make large developmental changes in an organism which might case a radically different phenotype. However, manipulating "Hox" genes does little to solve the problem of generating novel functional biostructures, for making large changes in phenotype are rarely beneficial. Hox gene mutations may be a more simple mechanism for generating large change, but they also do not escape the problem of the "hopeful monster":

"The drawback for scientists is that nature's shrewd economy conceals enormous complexity. Researchers are finding evidence that the Hox genes and the non-Hox homeobox genes are not independent agents but members of vast genetic networks that connect hundreds, perhaps thousands, of other genes. Change one component, and myriad others will change as well--and not necessarily for the better. Thus dreams of tinkering with nature's toolbox to bring to life what scientists call a "hopeful monster"- such as a fish with feet--are likely to remain elusive."

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