Provided herein are methods, systems, and compositions for seamless nucleic acid assembly. Methods, systems, and compositions as provided herein provide for efficient assembly of nucleic acids without primer removal. Methods, systems, and compositions for seamless nucleic acid assembly comprise use of an endonuclease or exonuclease, optionally in conjunction with additional enzymes to assemble nucleic acids or polynucleotides.

Provided herein are methods, systems, and compositions for efficient nucleic acid assembly. Nucleic acid assembly may comprise assembly of variants comprising paired homology.

Provided herein are methods, systems, and compositions for efficient nucleic acid assembly. Nucleic acid assembly may comprise assembly of variants comprising paired homology.

A method of amplifying a target polynucleotide, comprising: providing a template polynucleotide comprising a 5′ hairpin, a target polynucleotide and a 3′ hairpin, wherein the 5′ hairpin comprises one or more non-canonical nucleotides; and contacting the template polynucleotide with a polymerase and canonical nucleotides, wherein the polymerase extends, using the canonical nucleotides, the target polynucleotide from its 3′ end to form a first extended polynucleotide comprising the 5′ hairpin at its 5′ end and the complement of the 5′ hairpin at its 3′ end, wherein the complement of the 5′ hairpin forms a 3′ hairpin; and the polymerase extends the first extended polynucleotide from its 3′ end to form a second extended polynucleotide comprising the 5′ hairpin at its 5′ end and the complement of the 5′ hairpin at its 3′ end, wherein the complement of the 5′ hairpin forms a 3′ hairpin.

Aspects of the invention relate to methods, compositions for synthesizing oligonucleotides having a predefined sequence.

Synthetic auxotrophs with one or more ligand-dependent essential gene functions and methods of production that can be used for biosafety. The ligand-dependent function of an essential gene product can be produced by a series of mutations in the ORF of an essential gene; N, C, or insertional fusions of ligand-binding domains with essential genes or an engineered ligand-dependent intein splicing to alter essential gene function. A positive and/or negative selection can be used to identify auxotrophs from created mutant libraries. The positive selection is performed by growing a mutant library in conditions where growth or viability depends on the function of mutagenized essential genes. The negative selection eliminates constitutively growing cells that do not require a ligand for growth by growing the library in the absence of complementing ligand and in conditions where growing cells are eliminated. Desirable phenotypes are collected after the selections.

Methods and constructs for RNA-guided targeting of heterologous functional domains such as transcriptional activators to specific genomic loci.

Methods and apparatus relate to the synthesis of polynucleotides having a predefined sequence on a support. Assembly methods include primer extension to generate overlapping construction oligonucleotides and assembly of the polynucleotides of interest onto an anchor support-bound oligonucleotides. Methods and apparatus for selection of polynucleotides having the predefined sequence and/or length are disclosed.

A method for determining the number of nucleic acid molecules (NAMs) in a group of NAMs, comprising i) obtaining an amplified and mutagenized group of NAMs that was produced by a. subjecting the group of NAMs to a chemical mutagenesis which mutates only select nucleic acid bases in the group of NAMs at a rate of 10% to 90% thus forming a group of mutagenized NAMs (mNAMs), and b. amplifying the group of mNAMs; ii) obtaining sequences of the mNAMs in the group of amplified mNAMs; and iii) counting the number of different sequences obtained in step (ii) to determine the number of unique mNAMs in the group of mNAMS,

thereby determining the number of NAMs in the group of NAMs.

The invention provides compositions and methods for assembling a DNA molecule having a desired sequence. The methods involve contacting a DNA polymerase, dNTPs, and a plurality of pairs of oligonucleotides. The oligonucleotides of a pair have a portion of the desired sequence, and an internal sequence that overlaps and is complementary to an internal sequence of the other oligonucleotide of the pair, and, when arranged in order, they have at least a portion of the desired sequence. The oligonucleotides also have a 3′ or a 5′ primer binding sequence having a binding site for a primer. The oligonucleotides that correspond to the end oligonucleotides of the desired sequence also have a universal 3′ flanking sequence and a universal 5′ flanking sequence, respectively.