Do homologous chromosomes differ? A preliminary investigation based on DNA measurements

This paper is concerned with the problem of deciding whether measurements from homologous chromosomes differ. First, a general mathematical model is proposed for studying the distribution of chromosome measurements. Next, log-likelihood ratios are used to test for correlation between homolog pairs and for differences between homolog means and variances. The tests are applied to measurments on 1946 pairs of chromosomes from 10 normal individuals. Test results are interpreted taking into account the large number (2025 total tests) required by the study. Our results demonstrate that, at the current level of resolution, most homologs do not show differences in DNA content. However, there is some evidence that several homologs pairs differ by small amounts of DNA (less than 0.2% of the autosomal genome). Power studies indicate that sample sizes of 20 to 30 measurements are required to detect differences of this size.