New estimates of intergenerational time intervals for the calculation of age and origins of mutations - PubMed (original) (raw)

New estimates of intergenerational time intervals for the calculation of age and origins of mutations

M Tremblay et al. Am J Hum Genet. 2000 Feb.

Abstract

Intergenerational time intervals are frequently used in human population-genetics studies concerned with the ages and origins of mutations. In most cases, mean intervals of 20 or 25 years are used, regardless of the demographic characteristics of the population under study. Although these characteristics may vary from prehistoric to historical times, we suggest that this value is probably too low, and that the ages of some mutations may have been underestimated. Analyses were performed by using the BALSAC Population Register (Quebec, Canada), from which several intergenerational comparisons can be made. Family reconstitutions were used to measure interval lengths and variations in descending lineages. Various parameters were considered, such as spouse age at marriage, parental age, and reproduction levels. Mother-child and father-child intervals were compared. Intergenerational male and female intervals were also analyzed in 100 extended ascending genealogies. Results showed that a mean value of 30 years is a better estimate of intergenerational intervals than 20 or 25 years. As marked differences between male and female interval length were observed, specific values are proposed for mtDNA, autosomal, X-chromosomal, and Y-chromosomal loci. The applicability of these results for age estimates of mutations is discussed.

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Figures

Figure 1

Figure 1

Distribution of parents according to their ages at various events.

Figure 2

Figure 2

Mean numbers of children and married children according to parents' mean age at birth of children.

Figure 3

Figure 3

Distribution of the 10,558 distinct intergenerational intervals in the genealogies.

Figure 4

Figure 4

Distribution of the 100 genealogies according to mean length of intergenerational intervals.

Figure 5

Figure 5

Distribution of the 457 founders according to mean length of intergenerational intervals in their lineages.

Figure 6

Figure 6

Relation between founders' genetic contribution and mean length of intergenerational intervals in their lineages.

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