afdave
Posts: 1621 Joined: April 2006
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BASIC GENETICS REVIEW FOR ERIC AND OTHERS Now I hope no one is insulted by this title ... "Dave! Giving a refresher course in genetics! Guffaw!" And it is true that a few months ago I didn't even know the exact definition of an allele ... I just knew it had something to do with genes. But whether you are insulted or not, you should read this, because judging from some of your comments, I think I now have a better grip on basic genetics than some of you. I learn quickly. :-)
GENES, ALLELES AND HETEROZYGOSITY Terms we all have thrown around alot lately so we need to be clear about them. We turn to our trusty friend Wikipedia ... Quote | The terms Homozygous, Heterozygous and Hemizygous are used to simplify the description of the genotype of a diploid organism at a single genetic locus. At a given gene or position along a chromosome (a locus), the DNA sequence can vary among individuals in the population. The variable DNA segments are referred to as alleles, and diploid organisms generally have two alleles at each locus, one allele for each of the two homologous chromosomes. Simply stated, homozygous describes two identical alleles or DNA sequences at one locus, heterozygous describes two different alleles at one locus, and hemizygous describes the presence of only a single copy of the gene in an otherwise diploid organism.
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OK. So are we clear? A diploid organism (an individual) can have two alleles at each locus. If the alleles are the same -- homozygous. If different -- heterozygous.
COMMON (OR WILD) ALLELES, MUTATED ALLELES, RARE ALLELES So we understand individuals. What about populations? How many different alleles are there in typical diploid organism populations? The individual can only have two, but there could be many in a population from which two per individual are selected. As you would expect, someone has studied this -- G.S. Mani. According to him, most loci of present-day animals contain between 1 and 5 alleles (disregarding the MHC complex--separate topic discussed already). (Mani, G.S. 1984. "Darwinian theory of enzyme polymorphism (pp. 242-298) in Mani, G.S., ed., Evolutionary Dynamics of Genetic Diversity. Springer-Verlag, Berlin, Heidelberg, New York.) Woodmorappe notes ... Quote | Since most of the pre-Flood animal pairs could have carried 4 alleles per locus, this means that, in most cases, no mutations need have taken place since the Flood to generate the 1 to 5 alleles per locus seen today. Of course, most loci have fewer than 4 alleles per locus because the Ark animals did not always carry the maximum possible four per pair, and/or some alleles have been lost since the Flood by genetic drift. (Noah's Ark: A Feasability Study, p.195) | Also, there is a book with a very interesting title that I want to get: The History and Geography of Human Genes (1994) by L.L. Cavalli-Sforza et. al. This book (which is about humans, not sure if other mammals are discussed) has a table (pp. 8-9) that shows that the overwhelming majority of polymorphic loci have no more than four alleles per locus, very rare variants excepted. Continuing with info from Woodmorappe ... Furthermore, there is usually a single allele occurring at high frequency (at least 85%), with 1 to 3 other alleles found at frequencies of 1-15%. (MHC Polymorphism and the Design of Captive Breeding Programs - group of 4 »AL Hughes - Conservation Biology, 1991 - Blackwell Synergy, p. 249). In fact, of all alleles, most exist at low frequency (Considerations on the conservation of alleles and of genic heterozygosity in small managed … PA Fuerst, T Maruyama - Zoo Biology, 1986 - doi.wiley.com, p. 174). This is further borne out by the very definition of a polymorphic locus: one where the most common allele occurs at no more than 95% frequency in the population. (Inbreeding: one word, several meanings, much confusion. - group of 2 »AR Templeton, B Read - EXS, 1994 - ncbi.nlm.nih.gov, p. 60)
LET'S DO A LITTLE SPECULATING HERE FOR A MINUTE Notice I'm clearly labeling this part as speculation. I think it is possible that God originally created only two alleles per locus. I'm even more confident that He created no more than 4. But I think there is evidence that there were only 2 originally. Why do I think this? Several reasons. The info just given above about allele frequencies is a big one. Also, some (probably many) alleles are different from other alleles at only ONE nucleotide position indicating that there is an original designed allele and a mutated version of that same allele which was not designed. The eye color discussion below also makes me think this as you will see because all the various eye colors are controlled by only two different alleles at 3 (maybe more) loci. Of course, you think that ALL alleles were created by mutation and that is where we differ.
So to sum up this section, you read various terms associated with alleles such as "common" and "rare" and "wild" and "mutated." Quote | A wild type allele is an allele which is considered to be "normal" for the organism in question, as opposed to a mutant allele which is usually a relatively new modification. [Wikipedia "allele"] |
[URL=http://www.filecrunch.com/file....FD_CGH1
AFD_CGH2
I will update these when this thread is closed so you can have the complete thread.
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INCORYGIBLE'S REQUEST FOR AN OBJECTIVE STANDARD FOR CLASSIFYING ORGANISMS Quote | [Dave]Aren't all dog/wolf/coyote sequence differences miniscule?
[Cory]Yes. Which really makes them a rather poor example of genetic diversity emerging from small founding populations, eh? (You do know the difference between genotypes and phenotypes, right?) So if I was arguing that genetic diversity could arise rapidly (e.g., the genetic diversity we find among species of the same supposed 'kind' today), dogs certainly would not be my case study of choice. | I am arguing that phenotypic diversity can arise rapidly, not genetic diversity as measured by sequence differences. IOW, I am arguing that a single pair of the "dog/wolf" kind possessing a fair amount of heterozygosity (most common alleles included--yes, only 4 per pair, Eric) could rapidly diversify and generate the "dramatic differences" we see today in a very short time. This founder pair would probably look similar to one another and would be somewhere in the middle of either extremes for any given characteristics. This is what Ayala is speaking of when he talks about the "much larger reservoir of stored genetic variation." A vast amount of variation can be stored in just one founder pair with only two alleles per locus. As we have seen in the case of eye color in humans, only 2 alleles on two different genes (and likely only 2 different alleles on some as yet unknown other genes) cause a wide range of eye colors. Not lots of alleles as previously thought. Just several different genes, each with 2 different alleles is probably all that is required for massive diversity in every characteristic.
Quote | Dave, Hominidae is a FAMILY consisting of humans, chimps, gorillas and orangutans. You have stated that the created kinds were probably on the level of the FAMILY. Humans and chimps are actually two VERY CLOSELY RELATED species of the SAME FAMILY (much closer than the average distance between family members if we were to pick two species at random from some shared family). I asked for an OBJECTIVE STANDARD (no scripture, no handwaving about "non-biological" differences) by which we could confidently separate humans from (other) apes and yet still be able to group all those emerging family members after the flood into the same 'kind' in order to keep the ark's passenger list feasible. You suggested sequence differences, and I would agree. Problem is, those aren't going to separate humans and chimps (they would separate out the 'rangs and gorillas into separate kinds first). And if you want to use a figure of ~5% sequence divergence for your delineation of kinds, you can't fit the planet's biodiversity on the boat. You wouldn't be trying some special pleading when it comes to humans, would you? Because that's not allowed in an objective standard (or in rational debate).
So, if we figure that 'kind' ~ biological family, then it stands to reason that Adam and Eve (and by extension, God, given that whole "in His image" thing) were probably hairy apes, based on the shared characteristics of surviving members of this 'kind'. There's also a good chance that they were largely arboreal, which explains how they reached God's untouchable fruit (not to mention fruit-monopolization itself). No way of knowing if they shared the same fecal fascination exhibited by apes in captivity (does the garden count as captivity?). | Yes. I quoted Woodmorappe's opinion that the created kind probably was roughly equivalent to the family (at least in the case of mammals and birds). And you would have a very good point in asking how can we separate humans from the great apes if sequence difference is our objective guide .. EXCEPT ... for the fact that you are overlooking one key item.
You are disregarding two pieces of Biblical information ...
"Genesis 1: 26 ¶ Then God said, "Let Us make man in Our image, according to Our likeness; let them have dominion over the fish of the sea, over the birds of the air, and over the cattle, over all the earth and over every creeping thing that creeps on the earth." 27 So God created man in His own image; in the image of God He created him; male and female He created them. 28 Then God blessed them, and God said to them, "Be fruitful and multiply; fill the earth and subdue it; have dominion over the fish of the sea, over the birds of the air, and over every living thing that moves on the earth."
... and ...
"Genesis 2:7 And the LORD God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living being."
Now of course, you do not take these statements as authoritative, which is fine for now ... you will in time either in this life or the next, but nevertheless, even with your present dim view of the Genesis record, these passages stand as possible clues to the profound mystery of the differences we see between apes and humans.
"In the image of God?" "Breathed into his nostrils the breath of life?" Hmmm ... come to think of it, that's a pretty good description. Think about it. The Bible claims that God has creative ability, a will, a knowledge of right and wrong, and an appreciation for art and beauty, to name a few. Well ... guess what. Mankind has those characteristics also. And what animal do you know of that has these? Can you think of one? I cannot. So in a very real sense, we see agreement between some observations in the physical world and the record of Scripture. This is just one example, but it should give a thoughful person pause. There are many, many other examples of agreement between "God's World" and "God's Word." It's an exciting study!
But I'm sure that hearing this, you will accuse me of special pleading in my objective standard and I am afraid I will be found guilty, although as I think I can show, this special pleading is justified. As has been stated before, scientific evidence can only get us so far. (A lot farther that many Bible believers think, but still only so far.
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A NOTE ABOUT WHAT WE CAN PROVE AND WHAT WE CANNOT PROVE I noticed some interesting discussion on the "DGSVWEDA THREAD" about items taken on faith and items not taken on faith and this relates somewhat to this Ape/Human discussion.
I think it is very important to note that neither side of the current debate -- Evolutionist or Creationist -- can prove exactly how "Goddidit" or how "Evolutiondidit" whether we are talking about Apes and Humans or the Flood or the exact demarcation of kinds or what have you.
We are both in the predicament of being a little like detectives investigating a crime scene.
But thankfully, there are a lot of clues. And in my study of science and history, I have found that overwhelmingly, the clues point toward the truth of the Genesis Record.
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A NOTE ABOUT FUTURE DEBATES I am considering where to "set up shop" next. Thanks to Steve Story for the suggestion to go to http://richarddawkins.net/forum/index.php He says they have huge traffic and this may be perfect for me. Second choice would be at my own blog airdave.blogspot.com If I do that, I would welcome anyone from here and would of course open up comments. And I may do both. We shall see. As you can tell from Steve's efforts, moderating comments can involve some work and I'm not sure I want that workload. In any case, I have many topics yet to cover (including about 35 questions still to go on the Deadman "50" List, the Ice Age and Ice Cores, the Tower of Babel and the founding of China and Egypt, questions like Argy's parasites and "Did Adam and Eve have an immune system" etc.)
******************************************** MY NEW FAVORITE WORD Unbe-smegging-lievable. Thanks, Tim.
-------------- A DILEMMA FOR THE COMMITTED NATURALIST
A Hi-tech alien spaceship lands on earth ... DESIGNED.
A Hi-tech alien rotary motor found in a cell ... NOT DESIGNED.
http://afdave.wordpress.com/....ess.com
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