Cosmid vectors

Claim 2

A cosmid vector comprising at least three cos of X-phage or lambdoid phage in tandem.

Claim 3

A cosmid vector according to claim 1 which contains a respective cleavage site for each of two restriction endonucleases such that, on digestion of the cosmid vector with the said restriction endonucleases, the cosmid vector is cleaved into left and right arms wherein one arm comprises at least one cos and the other arm comprises two cos.

Claim 4

A cosmid vector according to claim 2, wherein the arms are of approximately equal length.

Claim 5

A cosmid vector according to claim 2 or 3, wherein the right arm comprises at least one cos and the left arm comprises two cos.

Claim 6

A cosmid vector according to any one of the preceding claims, which comprisesthree cos.

Claim 7

A cosmid vector according to any one of the preceding claims, which comprises a marker gene coding for the expression of drug resistance or for a specific physiological function.

Claim 8

A cosmid vector according to claim 6, wherein the drug resistance is ampicillin resistance, tetracycline resistance, neomycin resistance or chloramphenicol resistance.

Claim 9

A cosmid vector according to claim 6, wherein the said physiological function is thymidine kinase (TK) activity, adenine phosphoribosyl transferase (APRT) activity, hypoxanthine guanine phosphoribosyl transferase (HGPRT) activity, xanthine guanine phosphoribosyl transferase (XGPRT or gpt) activity or dihydrofolic acid reductase (dhfr) activity.

Claim 10

A cosmid vector according to any one of the preceding claims, which comprises a gene region having a replication function originating from ColEI.

Claim 11

A process for preparing a gene bank which process comprises: (i) cleaving a cosmid vector as claimed in any one of the preceding claims into left and right arms by digesting the cosmid vector with two restriction endonucleases, one arm having at least one cos and the other having two cos; (ii) ligating extraneous DNA fragments of 35 - 45 Kbp between respective pairs of left and right arms; (iii) packaging the recombinant DNA thus prepared as transducing phage particles by means of in vitro packaging and infecting X-phage lysogenic Escherichia coli with the said particles; and (iv) after cloning, inducting an E. coli transformant to package the recombinant DNA contained therein as transducing phage particles.

Claim 12

A process according to claim 10, wherein the extraneous DNA is a DNA from a microorganism, animal or plant.

Claim 13

A drug-resistant cosmid vector comprising two cos of λ-phage or lambdoid phage in tandem and containing a respective cleavage site for each of the two restriction endonucleases such that, on digestion of the cosmid vector with the said restriction endonucleases, the cosmid vector is cleaved into two arms each having one cos.

Claim 14

A drug-resistant cosmid vector comprising two cos of λ-phage or lambdoid phage in tandem and containing a respective cleavage site for each of the two restriction endonucleases such that, on digestion of the cosmid vector with the said restriction endonucleases, the cosmid vector is cleaved into two arms each having one cos.

Claim 15

A microorganism transformed with a cosmid vector as claimed in any one of claims 1 to 9.

Claim 16

Use of a cosmid vector as claimed in any one of claims 1 to 9 in the preparation of a gene bank by cosmid cloning.

Claim 17

Escherichia coli HB101-pTcos A p r /ori/cm r /neo r .

Claim 18

Escherichia coli HB101-pTcos A p r /ori/cm r /neo r .

Claim 19

Escherichia coli HB101-pTcos Ap r /ori/TK/cm r /neo r

Claim 20

Escherichia coli HB101-pTcos Ap r /ori/TK/cm r /neo r

Claim 21

Escherichia coli HB101-pD cos/cm r .

Claim 22

Escherichia coli HB101-pD cos/cm r .