Cohen Modal Cluster Haplotype

The Cohen Modal Cluster Haplotype

The Cohen Modal Cluster Haplotype (CMCH) is the name used to define a category that belongs to Cohanim males, J1 and J2, descendents from a commom ancestral type, strongly believed to be Aaron HaKohen, the first Priest, brother of Moses, and father of all Cohanim. Cohanim chromosomes are homogeneous. What characterize the Cohen Modal Cluster Haplotype(CMCH) is a Y-Chromossome-Especific variation at six micro-satellites (repeats of short nucleotides sequences) called Unique Event Polymorphism which is a genetic marker that corresponds to a mutation that is so infrequently, that all individuals who share the marker, worldwide, have inherited it from the same common ancestor, and the same single mutation event.

Examples

Because of microsatellite instability, it was useful to define a COHEN MODAL CLUSTER, of six related chromosomes as the Cohen Modal Haplotype (CMH-6) used now as the standard signature and all of its one-mutation neighbours at the microsatellite loci, which all share the same Cohen Unique-Event Polymorphism (UEP).
The distribution of allele sizes within Cohen UEP group, at the trinucleotide microsatellite DYS388 indicates a departure from the stepwise mutation modal. Because this modal underlies the method used to estimate the coalescence time of Cohen chromosomes, the DYS388 was 'dropped' and not considerate from the analysis.

Example:DYS = 393 390 19 391 392
J1 Standard CMH- 12 23 14 10 11 (Cohen Unique-Event Polymorphism)
J2 Cohanim - 12 23 15 10 11 (Cohen Unique-Event Polymorphism)

Katz, Kaplan, Kaplansky, Kahan, Catznelson, Kohn, Myer HaKohen.

All members with those surnames above that were tested, turn to be 'positive' for the Cohen Modal Cluster Haplotype. They all share the same Cohen Unique-Event Polymorphism and have the J2 Cohanim signature above.

Any one-mutation neighbours from the J1 Standard (CMH) above is considerate from the same Cohen Unique-Event Polymorphism (UEP). Those who macth the Cohen Unique-Event Polymorphism belongs to the single Cohen Modal Cluster Haplotype (CMCH).
PS: Even counting the DYS388 as an one-step mutation either on the stepwise modal or infinite alleles modal, those J2 Cohanim above still share the Cohen Unique-Event Polymorphism, because their values in DYS388=15 rather than 16 of the J1 CHM Standard 6 marks.

Coalescence Time

It is interesting to estimate the correct time at which Cohen chromossomes were derived from a commom ancestral chromossome (coalescence time). Under 'stepwise mutations' the average squared difference (ASD) in allele size among all current chromossome and the ancestral haplotype, averaged over loci, has an expectation of T, where is the mutation rate and T the coalescence time. Taking the Ashkenazic and Sephardic Communities as a whole, the value for ASD is 0.2226. Assuming a mutation rate of 0.0021, this gives a estimate of 106 generations time of 25 (30) years gives an estimate of 2,619 (3,180) years before present, dating the coalescence of the Cohanim chromossomes to between the Exodus and the destruction of the first Temple in 586 BC. Estimates based on the Ashkenazic and Sephardic samples taken separately are 2,619 (3,142) and 2,684 (3,221) years before present, respectively. To obtain confidence intervals on the distance between the ancestral and sampled chromossomes, it was noted that most non-ancestral haplotypes are singletons, indicating that the genealogy connecting Cohen chromossomes is more like the 'star genealogy' characteristic of 'rapid growth' than the other correlated genalogy characteristic of constant size populations. To obtain true confidence intervals in this case, (M) mutations occur during the 106 generations, with (M) being a Poisson random variable with parameter 106. The number of mutations increasing allele size (D) is drawn from a binomial distribution with parameters 0.5 and (M) leading to the distance D (2dm). In a star genealogy, there are 485 (the number of loci multiplied by the sample size) observations of D. Confidence intervals are obtained by repeating this process 1,000 times and taking the associated 2.5 and 97.5 pecentiles, leading to a 95% confidence interval of 84-130 generations for the combined Ashkenazic and Sephardic samples or for a generations time of 25 years, only 2,100-3,250 years before present. The 95% confidence interval places the origin of priestly Y-Chromossomes, in J1 and J2, sometime during or shortly before the first Temple period in Jewish history (2,100-3,250).According to Jewish Tradition, following the Exodus from Egypt, the tribe of Levi, of which Moses was a member, were assigned special religious responsabilities, and males descendents of Aaron, his brother, were selected to serve as Priests (Cohanim).

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