Figure 6.

Instability of C arrays and their prevalence in MS1 alleles. A, Sperm mutation rates in C arrays deduced from SM-PCR analysis of allele A in man 1, under the assumption that mutation steps always involve the loss of a single C-type repeat. No deletions were seen in the two C₂, three C₃, and two C₄ arrays in this allele, giving a mean mutation rate of <0.005 per array (P>.95). The estimate for C₁₂ arrays was taken from the incidence of deletions in this array in large mutants characterized in man 2 (see fig. 3). B, Abundance of C arrays in MS1 alleles. The distribution was determined from alleles in men 1 and 2 and from 10 additional short alleles (64–155 repeats) from northern European men who were fully typed by MVR-PCR (1,720 repeats typed in total, data not shown). For comparison, the abundance of A-repeat clusters is also shown. The log-linear relationship (gray line) between abundance and short array length (<10 repeats) is the same for C- and A-type repeats.