R2d2 and Hyperdrive Mechanisms (in Mouse Meiosis)
Figure 1
Transmission ratio distortion (TRD) caused by a high copy R2d2 array.
In the absence of the R2d2 sequence (e.g., C57BL/6J), or when the copy number of the sequence is low (e.g., CAST/EiJ), allele transmission through heterozygous females is Mendelian and no embryonic lethality is observed. When the copy number is high in the appropriate genetic background (e.g. WSB/EiJ), the litter sizes of heterozygous females are reduced and the R2d2 locus shows TRD. When the copy number of R2d2 repeats decreases (e.g., DO-G13–44), litter sizes increase and Mendelian segregation is restored.