RT Journal Article
SR Electronic
T1 Signatures of Population Expansion in Microsatellite Repeat Data
JF Genetics
JO Genetics
FD Genetics Society of America
SP 1921
OP 1930
VO 148
IS 4
A1 Kimmel, Marek
A1 Chakraborty, Ranajit
A1 King, J. Patrick
A1 Bamshad, Michael
A1 Watkins, W. Scott
A1 Jorde, Lynn B.
YR 1998
UL http://www.genetics.org/content/148/4/1921.abstract
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 modern 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.