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Gene Conversion Violates the Stepwise Mutation Model for Microsatellites in Y ‐Chromosomal Palindromic Repeats
Author(s) -
Balaresque Patricia,
King Turi E.,
Parkin Emma J.,
Heyer Evelyne,
CarvalhoSilva Denise,
Kraaijenbrink Thirsa,
Knijff Peter,
TylerSmith Chris,
Jobling Mark A.
Publication year - 2014
Publication title -
human mutation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 162
eISSN - 1098-1004
pISSN - 1059-7794
DOI - 10.1002/humu.22542
Subject(s) - biology , palindrome , microsatellite , genetics , gene conversion , tandem repeat , mutation rate , gene , haplogroup , direct repeat , chromosome , haplotype , mutation , allele , genome
The male‐specific region of the human Y chromosome ( MSY ) contains eight large inverted repeats (palindromes), in which high‐sequence similarity between repeat arms is maintained by gene conversion. These palindromes also harbor microsatellites, considered to evolve via a stepwise mutation model ( SMM ). Here, we ask whether gene conversion between palindrome microsatellites contributes to their mutational dynamics. First, we study the duplicated tetranucleotide microsatellite DYS 385a,b lying in palindrome P 4. We show, by comparing observed data with simulated data under a SMM within haplogroups, that observed heteroallelic combinations in which the modal repeat number difference between copies was large, can give rise to homoallelic combinations with zero‐repeats difference, equivalent to many single‐step mutations. These are unlikely to be generated under a strict SMM , suggesting the action of gene conversion. Second, we show that the intercopy repeat number difference for a large set of duplicated microsatellites in all palindromes in the MSY reference sequence is significantly reduced compared with that for nonpalindrome‐duplicated microsatellites, suggesting that the former are characterized by unusual evolutionary dynamics. These observations indicate that gene conversion violates the SMM for microsatellites in palindromes, homogenizing copies within individual Y chromosomes, but increasing overall haplotype diversity among chromosomes within related groups.