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The ZFN-encoding mRNA was injected into one-cell embryos and a high percentage of animals carried the desired mutations and phenotypes. Their research work demonstrated that ZFNs can specifically and efficiently create heritable mutant alleles at loci of interest in the germ line, and ZFN-induced alleles can be propagated in subsequent generations.
Three possible sub-pathways for a double-strand break to repair via homologous recombination: Gene conversion, BIR and SDSA. The gene conversion is referring to the double-strand break repair model. The other sub-pathway is the synthesis-dependent strain annealing. SSA is the fourth sub-pathway and it is not shown in this diagram.
Zinc fingers were first identified in a study of transcription in the African clawed frog, Xenopus laevis in the laboratory of Aaron Klug.A study of the transcription of a particular RNA sequence revealed that the binding strength of a small transcription factor (transcription factor IIIA; TFIIIA) was due to the presence of zinc-coordinating finger-like structures. [6]
MUS81/EME1 is a structure specific endonuclease involved in converting interstrand crosslinks to double-strand breaks in a DNA replication-dependent manner. [12] After introduction of a double-strand break, further steps are required to complete the repair process. If a crosslink is not properly repaired it can block DNA replication. [citation ...
Strand exchange then proceeds via a crossed strand intermediate analogous to the Holliday junction in which only one pair of strands has been exchanged. [15] [16] The mechanism and control of serine recombinases is much less well understood. This group of enzymes was only discovered in the mid-1990s and is still relatively small.
The dimerization of two ZFNs is required to produce the necessary double-strand break within the CCR5 gene because the interaction between the FokI enzyme and DNA is weak. [11] This break is repaired by the natural repair mechanisms of the cell, specifically non-homologous end joining. [11]
Tandem DNA lesions are formed at a substantial frequency by ionizing radiation and metal-catalyzed H 2 O 2 reactions. Under anoxic conditions, the predominant double-base lesion is a species in which the C8 of guanine is linked to the 5-methyl group of an adjacent 3'-thymine (G[8,5- Me]T), forming intrastrand lesions.
The mechanism of the ligation reaction was first elucidated in the laboratory of I. Robert Lehman. [4] [5] Two fragments of DNA may be joined by DNA ligase which catalyzes the formation of a phosphodiester bond between the 3'-hydroxyl group (-OH) at one end of a strand of DNA and the 5'-phosphate group (-PO4) of another.