What is the difference between Alt-R™ HDR Donor Blocks and Megamer™ Single-Stranded DNA Fragments?
The Alt-R HDR Donor Block and Megamer products are both intended to generate CRISPR-mediated insertions. Alt-R HDR Donor Blocks are chemically modified dsDNA repair templates while Megamer Single-Stranded DNA Fragments are long ssDNA repair templates. Megamer fragments are also chemically modified templates, however, their modification is different than that of HDR Donor Blocks. Due to the differences in manufacturing, Megamers are limited in yield (3 µg standard) and can be more costly. Alt-R HDR Donor Blocks are available at larger yields that are typically required for cell culture work (3 or 10 µg standard) and offer a more cost-effective solution. While both products can be used to create CRISPR knock-ins, several differences in repair outcomes have been observed between dsDNA and ssDNA repair templates.
First, ssDNA innately has a lower risk of non-homologous end joining (NHEJ) mediated insertion compared to unmodified dsDNA. IDT’s proprietary modifications help mitigate that risk when using an Alt-R HDR Donor Block. Second, long ssDNA repair templates can result in incomplete HDR insertions. This does not occur frequently with dsDNA templates such as Alt-R HDR Donor Blocks.
Finally, HDR (homology-directed repair) outcomes may be impacted by foreign DNA of a particular system. While successful HDR has been observed using both products in most systems tested, the ideal donor template may vary with the application and the cell line or system of choice.
Doc ID# RUO22-0951_001-4