Tightly linked di- and tri-nucleotide microsatellites do not evolve in complete independence: evidence from linked (TA) n and (TAA) n microsatellites of chickpea (Cicer arietinum L.)

Udupa, Sripada M.

Tightly linked di- and tri-nucleotide microsatellites do not evolve in complete independence: evidence from linked (TA) n and (TAA) n microsatellites of chickpea (Cicer arietinum L.)

Views

0% 0

Downloads

0 0%

Timeless limited access

Date

2003-10-16

Date Issued

2004-02-01

ISI Journal

Impact factor: 4.439 (Year: 2003)

Authors

Citation

Sripada M. Udupa, R Malhotra, Michael Baum. (1/2/2004). Tightly linked di- and tri-nucleotide microsatellites do not evolve in complete independence: evidence from linked (TA) n and (TAA) n microsatellites of chickpea (Cicer arietinum L. ). TAG Theoretical and Applied Genetics, 108 (3), pp. 550-557.

Abstract

In order to understand the dynamics of microsatellite evolution, we have studied allelic variation at a closely linked (TA) n and (TAA) n microsatellite loci in 114 land races of chickpea (Cicer arietinum L.), sampled worldwide. These two loci are separated by 27 bp. The two loci showed a very high degree of polymorphism and hence the combined length with the genetic diversity of 0.93, 0.90 and 0.98 for (TAA) n , (TA) n and the combined length, respectively. Using the variation data at the linked loci, a standardized index of linkage disequilibrium was also computed (I S A =0.092), which tests the null hypothesis of no linkage and was significant, indicating the presence of linkage disequilibrium. Furthermore, the dynamics of allelic variation showed that there is a threshold combined length, below which both (TAA) n and (TA) n loci evolve independently, and above which, if one locus increase in size, the other closely linked locus has a tendency to decrease its size and vice versa, without change in the overall ratio of (TAA) n and (TA) n allele sizes at the region. This result indicates that there are processes in the cell, which ‘read’ the combined size of the two loci both for proportion and length and determine the direction of tightly linked di- and tri-nucleotide repeat evolution.