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Searching for: +path:genealogy-dna +(+date:jul +date:2002)
Viewing 1-25 of 565 matches from 36,222,914 documents1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 | Next
1. Re: [DNA] Mutation? [1]
J.R. wrote: > There has been a mutation in descendants > of one son. I know this is only suppose to happen > every 500 generations but we were apparently lucky No, not every 500 generations, but that often at each locus. If you're testing 12 loci, you would expect a mutation every 40 generations or so. > I presume one testicular cell gives off sperm with > a mutation which could go to any of his sons and That's not quite how it works. Sperm cells result from the division of precursor cells, but the pre
2. Re: [DNA] Re: GENEALOGY-DNA-D Digest V02 #287 [1]
Mary wrote: > 1. Is it better to get a DNA sample from a 90-year-old father, or his > 50-year-old son, or even a 25-year-old grandson, in terms of trying to > minimize the liklihood of mutations? There are two separate things going on here: somatic mutations ("spot" mutations in individual cells here and there in the body) and generational mutations (changes in the reproductive cells that happen to lead to a new organism). The DNA tests provided by the testing companies operate on large numbers of cells
3. Re: [DNA] DYS meaning [1]
Several people have quoted John Butler to this effect: > Did you ever wonder what DYS stands for? D = DNA, Y = Y-chromosome, S = > (unique) segment [or "single copy sequence" according to "Forensic DNA > Typing" by John Butler]. The DYS numbering scheme (e.g. DYS388, DYS390) > for > the Y-STR haplotype loci is controlled and administered by an > international > standards body called HUGO Human Gene Nomenclature Committee based at > University College, London. Since all the DYS loci are in fact STRs, and si
4. Re: [DNA] UEP mutation rate [1]
Peter wrote: > I thought the occurrence of these were not that > high at all. What are the odds for these? "These" are just the usual mutations that we talk about all the time on this list. The odds are 1 in 500 per locus per generation. If you compare that with the 1 in a billion odds for a sinble base substitution error, you can see that the STR mutations are very common indeed in the grand scale of things, even though 1 in 500 sounds pretty low. John Chandler
5. Re: [DNA] 25 Marker loci & MRCA [1]
Ann wrote: > I agree that this seems odd. I'm not sure what the best method is to evaluate > this statistically -- maybe John C will step in here, but I'll lay out my > thoughts in the meantime. Ok, one last message, and then I'll be off for a couple of weeks. > Now those are two examples where there were more mutations in the additional > markers than in the original set. Keep in mind that we're looking at a biased > sample -- there may be examples out there where the opposite is true. > However, if ther
6. Re: [DNA] Poisson vs. others [1]
Jim wrote: > >N!/M!/(N-M)! > > Would that be the same as: > N! > -- X (N-M)! > M! No, the rule is: always perform divisions and multiplications as written from left to right, unless parentheses have been inserted to indicate otherwise. > >the median is 28.9 generations between the two > >endpoints, or 14.4 back to the MRCA > > so "median" must mean "50% chance". > > So there is a 50% chance of one of 12 markers will > fail (be off by one) if it is 14.4 generations back > to two testees' most recent common
7. Re: [DNA] Lovett Line Questions - All Thoughts requested and suggestions as to what to do next. [1]
Sheryl wrote: > We have two Edom Lovett (paper and dna) documented cousin members of the > same line match 12/12. They are off by 1 mutation at dys 391 > from the Benjamin Lovette line. Is the automatic conclusion that > there should be a 21/21 That depends on whether you can prove Edom was related to Benjamin by conventional means. If not, then you probably need the higher resolution (which is now up to 25 instead of 21, by the way). > If a 21/21 is run, the same mutation will be evident with
8. Re: [DNA] questions in FAQ [1]
Pieter wrote: > 1. A few years ago the scientific labs started with 4 markers on the Y > Chrom, then it became 6, then 8 ... > When is enough enough? The effort (and therefore the cost) rises in proportion to the number of markers tested, but the resolving power rises as the square root. The optimum thus depends on how much resolution you need vs how much you can afford. > 2. In surname projects, apart from a 100 % match, what is still an > acepptable mutation were one does not say : no family link bec
9. Re: [DNA] MRCA calculations, sperm, and phone calls [1]
Gregg wrote: > I still don't see any reason that > Poisson would not be applicable in the DYS mutation cases. It seems to me > that you only need to satisfy the Poisson assumptions. True, and that's exactly the problem here. I'm arguing that germ-line mutations do NOT satisfy the assumptions. In particular, Poisson assumes that the event in question is equally likely to occur in any time span of equal length. The Y DNA mutation transmissions occur only at the time of fertilization, i.e., only one oppor
10. Re: [DNA] Lovett Line Questions - All Thoughts requested and suggestions as to what to do next. [1]
Sheryl wrote: > Wouldn't the full 25/25 spectrum be looked at or do we discard the > results from the 12/12 altogether? The first 12 loci are not thrown away, but they don't get retested. If you order the upgrade from 12 to 25, they test 13 more loci and tack them onto the end of your report. John Chandler
11. Re: [DNA] questions in FAQ [1]
Pieter wrote: > Yet the term "meisoses" baffles me. What does it mean? The term meiosis (plural meioses) is used for the type of cell division that leads to egg and sperm cells, as opposed to mitosis (the usual kind) John Chandler
12. Re: [DNA] RelGen and DYS385 & YCAII [1]
Patrick wrote: > Yes I understand that, but surely the organisers will have checked > that only a well-established and tested (say) 'primer set 1' is being > used by the lab for the PCR 'cooking' and applies in all cases? It's one thing to check and another to know. On two occasions, I asked Diahan what primers she was using, but she was vague and never said. Meanwhile, from the message posted yesterday, with a response from "Katie", it would appear that the primers are indeed standard and that the map f
13. Re: [DNA] MRCA calculations, sperm, and phone calls [1]
Ann wrote: > For what it's worth, I've brought up Poisson distributions in a different > context, the number of mutations "expected" given a known number of > transmission events. This is the method Greg Bonner used on his Lentz/Lance > project summary, and it seems to me that the Poisson distribution is applied > correctly there. The problem is that the generation is an indivisible unit: there is no physical expression of any state between a father and his son. There may be other sons, but they are, by
14. Re: [DNA] Poisson vs. others [1]
Gregg wrote: > I don't know any other way. In my case, I can calculate 432! on other > computers which are readily available to me. Nevertheless, I would be > interested to learn how to determine exact binomial without having to > determine the (n) factorial. The point is that the binomial coefficient "N take M" is N!/M!/(N-M)!, and that expression is all you need. You don't need the individual factors. Therefore, if you find yourself in the regime where M is close to N, you note that N!/M! = Nx(N-1)x(N-
15. Re: [DNA] Relative Genetics Markers [1]
John Walden wrote: > If we make some assumptions about the markers being uncorrelated ... As Ann has already pointed out, the markers are very much correlated. That is why it took so long for someone to notice that Y-GATA A4 is actually the same thing as DYS439 and why DYS394 was assigned its own new number despite being the same thing as DYS19. John Chandler
16. Re: [DNA] Re: MRCA and FTDNA [1]
Lloyd wrote: > For a 12/12 match (.002) at 95 % FTDNA shows 62 generations while our > MRCA site shows 76.9 generations. A substantial difference in years ! "Our" MRCA site? Perhaps you mean Ann's MRCA calculator? As I understand it, her algorithm assumes a Poisson distribution for the number of mutations. Basically, this means that the time line is treated as a continuum, and a mutation is deemed equally likely to occur in any time segment of the same length as another segment. This is a good model fo
17. Re: [DNA] Poisson vs. others [1]
Gregg wrote: > that exact binomial will be impossible to use as a practical matter in many > cases. Sorry, Gregg, but that's a red herring. The binomial formula is used as a practical matter all the time in all cases. It's just a matter of using sensible impelementations. (Hint: the binomial coefficient is NOT calculated by taking three factorials and then dividing.) John Chandler
18. Re: [DNA] Population distribution of Rel Gen markers [1]
Dennis wrote: > What appears is a bi-modal ("two-humped") distribution... > Anybody have an educated guess? What are we seeing here - HG1 and HG2? Yes, that's it. The big studies all seem to have samples from both those haplogroups. John Chandler
19. Re: [DNA] MRCA calculations, sperm, and phone calls [1]
Ann wrote: > I don't follow your objection to the use of the generation as a unit of > measurement The objection is not to the generation as a time unit, but rather to the application of Poisson statistics to a phenomenon with a quantized time variable. In the studies people are actually doing, 10 generations is a typical scale (representing approximately the time span from American colonists to the present). > Could you write up your method for calculating the MRCA in such a way that > anyone with a cal
20. Re: [DNA] Population distribution of Rel Gen markers [1]
Phil wrote: > We match on 17 out of 23 loci (assuming DSY439 and Y-GATA-A4 are really the > same), which I realize could just happen by random (especially since two of > the differences seem to be two steps). Is there still a possibility that we > shared a common ancestor a millennia or two ago--perhaps even at the time > the name Ritter was given to various knights during the crusades? It's possible, but not likely. Since the mutations are starting to pile up here, you need to account for possible cancel
21. Re: [DNA] Relative Genetics Markers [1]
Ann wrote: > which suggests that DYS439 and Y-GATA A4 are actually the same > marker. But I've noted one exception where values were different (Alan > Gleason). By golly! I have a collection of 47 results extracted from emails to the list and web sites, and I see the same thing as well. Alan's stands out as the exception, but remember that his results were from before the calibration effort. Now that the case has been made, I can see that the primers listed on the NIST web site for DYS439 do indeed line
22. Re: [DNA] Getting Involved [1]
Phil wrote: > Is there something > different about the higher DSY numbers and the YCA and GGAAT that would > make them more variable? Good question. There is some evidence that longer STRs have higher mutation rates. There may be other trends as well, but the evidence is too sparse to discern them. > Has anyone posted variability for different loci > (variances or S.D.'s)? It's not clear how that would help. We cannot assume that the "starting" conditions were the same for each locus (e.g., all on
23. Re: [DNA] MRCA calculations, sperm, and phone calls [1]
Gregg wrote: > Why would this make a difference? Let me make an analogy. Let's say you want > to predict the probability of each of a range of numbers of phone calls you > will observe in a discrete amount of time, knowing what is the average > number of phone calls you observe in some much longer defined period of > time. So you apply Poisson and get answers. This is a bad analogy for several reasons. First, phone calls are far from random, with obvious daily and weekly cycles. It's not just coincidenc
24. Re: [DNA] Introductory Site [1]
Nancy wrote: > What questions should I include in a frequently asked questions section? The number-one question is, unfortunately, "Ok, here's my DNA test result -- what does that tell me?" Even though it can't be answered with a general answer, it should probably be included in the FAQ file with pointers to resources. A lot of the questions that come up can be answered by having a good glossary. You can sum them up by writing a single question in the form Q: What's a(n) [allele, base, buccal sample, ch
25. Re: [DNA] RFLP siblingship tests [1]
Ann wrote: > > Allele Values > > -------------------------------------------------------------------- > > marker ME Sib1 Sib2 Sib3 Sib4 Sib5 > > > > D2S44 3.11 3.11 1.58 3.11 1.75 1.58 > > 1.58 1.75 1.28 1.75 1.58 1.28 > > > > D4S163 4.49 5.11 4.49 5.11 4.49 5.11 > > 3.20 4.49 1.68 4.49 1.68 4.49 > > > > D6S132 2
Viewing 1-25 of 565 matches from 36,222,914 documents1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 | Next

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