TY - JOUR

T1 - Signatures of population expansion in microsatellite repeat data

AU - Kimmel, Marek

AU - Chakraborty, Ranajit

AU - King, J. Patrick

AU - Bamshad, Michael

AU - Watkins, W. Scott

AU - Jorde, Lynn B.

PY - 1998/4

Y1 - 1998/4

N2 - To examine the signature of population expansion on genetic variability at microsatellite loci, we consider a population that evolves according to the time-continuous Moran model, with growing population size and mutations that follow a general asymmetric stepwise mutation model. We present calculations of expected allele-size variance and homozygosity at a locus in such a model for several variants of growth, including stepwise, exponential, and logistic growth. These calculations in particular prove that population bottleneck followed by growth in size causes an imbalance between allele size variance and heterozygosity, characterized by the variance being transiently higher than expected under equilibrium conditions. This effect is, in a sense, analogous to that demonstrated before for the infinite allele model, where the number of alleles transiently increases after a stepwise growth of population. We analyze a set of data on tetranucleotide repeats that reveals the imbalance expected under the assumption of bottleneck followed by population growth in two out of three major racial groups. The imbalance is strongest in Asians, intermediate in Europeans, and absent in Africans. This finding is consistent with previous findings by others concerning the population expansion of modem humans, with the bottleneck event being most ancient in Africans, most recent in Asians, and intermediate in Europeans. Nevertheless, the imbalance index alone cannot reliably estimate the time of initiation of population expansion.

AB - To examine the signature of population expansion on genetic variability at microsatellite loci, we consider a population that evolves according to the time-continuous Moran model, with growing population size and mutations that follow a general asymmetric stepwise mutation model. We present calculations of expected allele-size variance and homozygosity at a locus in such a model for several variants of growth, including stepwise, exponential, and logistic growth. These calculations in particular prove that population bottleneck followed by growth in size causes an imbalance between allele size variance and heterozygosity, characterized by the variance being transiently higher than expected under equilibrium conditions. This effect is, in a sense, analogous to that demonstrated before for the infinite allele model, where the number of alleles transiently increases after a stepwise growth of population. We analyze a set of data on tetranucleotide repeats that reveals the imbalance expected under the assumption of bottleneck followed by population growth in two out of three major racial groups. The imbalance is strongest in Asians, intermediate in Europeans, and absent in Africans. This finding is consistent with previous findings by others concerning the population expansion of modem humans, with the bottleneck event being most ancient in Africans, most recent in Asians, and intermediate in Europeans. Nevertheless, the imbalance index alone cannot reliably estimate the time of initiation of population expansion.

UR - http://www.scopus.com/inward/record.url?scp=0031916646&partnerID=8YFLogxK

M3 - Article

C2 - 9560405

AN - SCOPUS:0031916646

VL - 148

SP - 1921

EP - 1930

JO - Genetics

JF - Genetics

SN - 0016-6731

IS - 4

ER -