pleiotropy
HURDLE NUMBER 28. THE PLEIOTROPY HURDLE.
The term “PLEIOTROPY” is defined (in the book Essential Genetics, by Anna Hodson, published by Bloomsbury Publishing Ltd., 1992) as follows:- “The condition in which a single mutant allele (ie:- for “allele” read “gene”) CAUSES A NUMBER OF DIFFERENT EFFECTS. These effects may be very diverse in their end result. - - - - - Many of the severe human disorders are examples of PLEIOTROPY, eg:- Marfan’s Syndrome, in which the primary defect in collagen synthesis leads not only to skeletal deformities, but to heart and eye defects.”
In the book The Biotic Message, by Walter James ReMine, published by St. Paul Science, 1993, page 178, the author tells us – “Pleiotropy is when genes affect more than one trait. For example, in flies there is a gene affecting eye color that also affects the reproductive system.”
The next quote is from the book Evolution a Theory in Crisis by Michael Denton (molecular biologist – He was a senior research fellow in the Biochemistry Department at the University of Otago, Dunedin, New Zealand from 1990 to 2005), published by Adler and Adler, 1986, pages 149 to 150:-
Denton discusses PLEIOTROPY. He quotes Ernst Mayr. (in his book Population, Species, and Evolution) (Mayr joined the faculty of Harvard University in 1953, where he also served as director of the Museum of Comparative Zoology from 1961 to 1970. He retired in 1975 as Emeritus Professor of Zoology.) who states that almost all genes are PLEIOTROPIC . “Non-pleiotropic genes must be rare, if they exist at all.”
Denton then comments:- “A mutation (in a single gene) causes developmental abnormalities in a variety of systems.”
The next quote is from Atlas of Creation, by Harun Yahya (Adrian Oktar), volume 2, 3rd edition, published by Global Publishing, Istanbul, page 605:-
The author discusses PLEIOTROPY. He argues that (for example) a mutation beneficial to eye development might also affect the stomach, PROBABLY ADVERSELY (since most mutations are harmful). A mutation that affects a number of organs ALL BENEFICIALLY IS VERY UNLIKELY. For an animal to evolve to (the presently observed) perfection, many thousands of PLEIOTROPIC mutations, all (improbably!) beneficial to all organs affected are required. The author argues that PLEIOTROPY presents a severe hurdle for the notion that evolution proceeds by random mutations. (My capitals.)
My comment:- PLEIOTROPY is a further “nail in the coffin” for the theory of “evolution” by random mutations. Most mutations are harmful. However, if a mutation “turned up” which was beneficial, if this mutation were PLEIOTROPIC (as is very highly probable), then it would also have adverse effects to counterbalance the beneficial effects.
An example illustrating this point is provided in The Oxford Dictionary of Biology, 6th edition, published by Oxford University Press, 2008. Under the entry – “Pleiotropic”, we are give an example of PLEIOTROPY:- “The allele that causes the erythrocytes to have a distorted form in sickle cell anemia also causes the blood cells to rupture easily, thereby inducing anemia”.
In the same book, under the entry – “Polymorphism”, we are told that sickle cell disease causes anemia (which is eventually fatal), but also provides resistance to some forms of malaria.
My comment:- This mutation is “beneficial” in providing resistance to malaria – but HARMFUL in causing anemia.
To summarize:- Most mutations are harmful. The very few that are beneficial are very likely to be PLEIOTROPIC, and therefore to be HARMFUL. The phenomenon of PLEIOTROPHY still further undermines the notion that “evolution” proceeds by random mutations.