Analysis of meiotic segregation, using single-sperm typing: meiotic drive at the myotonic dystrophy locus.
Meiotic drive at the myotonic dystrophy ( DM ) locus has recently been suggested as being responsible for maintaining the frequency , in the human population , of DM chromosomes capable of expansion to the disease state . In order to test this hypothesis , we have studied samples of single sperm from three individuals heterozygous at the DM locus , each with one allele larger and one allele smaller than 19 CTG repeats . To guard against the possible problem of differential PCR amplification rates based on the lengths of the alleles , the sperm were also typed at another closely linked marker whose allele size was unrelated to the allele size at the DM locus . Using statistical models specifically designed to study single-sperm segregation data , we find no evidence of meiotic segregation distortion . The upper limit of the two-sided 95 % confidence interval for the estimate of the common segregation probability for the three donors is at or below . 515 for all models considered , and no statistically significant difference from . 5 is detected in any of the models . This suggests that any greater amount of segregation distortion at the myotonic dystrophy locus must result from events following sperm ejaculation .
