Polymerases

1. A polymerase having amino acid sequence SEQ ID NO:22, having a substitution mutation at position Arg743 to a nonpolar amino acid or a substitution mutation at position Lys 705 to a nonpolar amino acid, whereby the polymerase has a reduced affinity for DNA.

2. The polymerase according to claim 1 , wherein the substitution mutation is a mutation at position Arg743.

3. The polymerase according to claim 2 , wherein the substitution mutation converts Arg743 to alanine (A).

4. The polymerase according to claim 1 , wherein the substitution mutation is a mutation at position Lys705.

5. The polymerase according to claim 3 , wherein the substitution mutation converts Lys705 to alanine (A).

6. A kit for performing a nucleotide incorporation reaction comprising: a polymerase as defined in claim 1 , and a nucleotide solution.

7. The kit of claim 6 , wherein the nucleotide solution comprises labelled nucleotides.

8. The kit of claim 6 , wherein the nucleotides comprise synthetic nucleotides.

9. The kit of claim 6 , wherein the nucleotides comprise modified nucleotides.

10. The kit of claim 9 , wherein the modified nucleotides have been modified at the 3′ sugar hydroxyl such that the substituent is larger in size than the naturally occurring 3′ hydroxyl group.

11. The kit according to claim 10 , wherein the modified nucleotides are a modified nucleotide or nucleoside molecule comprising a purine or pyrimidine base and a ribose or deoxyribose sugar moiety having a removable 3′-OH blocking group covalently attached thereto, such that the 3′ carbon atom has attached a group of the structure

—O—Z

wherein Z is any of —C(R′)2-O—R″, —C(R′)2-N(R″)2, —C(R)2-N(H)R″, —C(R)2-S—R″ and —C(R′)2-F,

wherein each R″ is or is part of a removable protecting group;

each R′ is independently a hydrogen atom, an alkyl, substituted alkyl, arylalkyl, alkenyl, alkynyl, aryl, heteroaryl, heterocyclic, acyl, cyano, alkoxy, aryloxy, heteroaryloxy or amido group, or a detectable label attached through a linking group; or (R′)2 represents an alkylidene group of formula ═C(R′″)2 wherein each R′″ may be the same or different and is selected from the group comprising hydrogen and halogen atoms and alkyl groups; and

wherein said molecule may be reacted to yield an intermediate in which each R″ is exchanged for H or, where Z is —C(R′)2-F, the F is exchanged for OH, SH or NH2, preferably OH, which intermediate dissociates under aqueous conditions to afford a molecule with a free 3′OH;

with the proviso that where Z is —C(R′)2-S—R″, both R′ groups are not H.

12. The kit according to claim 11 , wherein R′ of the modified nucleotide or nucleoside is an alkyl or substituted alkyl.

13. The kit according to claim 12 , wherein —Z of the modified nucleotide or nucleoside is of formula —C(R) 2 —N 3 .

14. The kit according to claim 13 , wherein Z is an azidomethyl group.

15. The kit according to claim 9 , wherein the modified nucleotides are fluorescently labelled to allow their detection.

16. The kit according to claim 9 , wherein the modified nucleotides comprise a nucleotide or nucleoside having a base attached to a detectable label via a cleavable linker, wherein the cleavable linker contains a moiety selected from the group consisting of:

wherein X is selected from the group comprising O, S, NH and NQ wherein Q is a C1-10 substituted or unsubstituted alkyl group, Y is selected from the group comprising O, S, NH and N(allyl), T is hydrogen or a C1-10 substituted or unsubstituted alkyl group and * indicates where the moiety is connected to the remainder of the nucleotide or nucleoside.

17. The kit according to claim 16 , wherein the detectable label comprises a fluorescent label.

18. The kit of claim 6 further comprising one or more DNA template molecules and/or primers.