An unidentified DNA segment which seems to be an insertion sequence element was isolated from $\underline{E.}$ $\underline{coli}$ K12 strain. It was inserted into the hybrid plasmid consisting of pBR322 and $\underline{trg}$ gene which codes for $\underline{E.}$ $\underline{coli}$ chemosensory transduer during the transfer of chromosomal $\underline{trg}$ mutation to plasmid via Hfr-mediated conduction.
The size of the unidentified DNA segment was estimated to be about 1.5 Kilobase pairs, and its restriction map was constructed. It has one Bgl II and one Hind III restriction enzyme cleavage sites.
The integration frequency of the plasmid containg unidentified segment into the chromosome of Hfr $\underline{polAts}$ strain of $\underline{E.}$ $\underline{coli}$ was 10,000 times greater than the plamsid without any inserted segment. The frequency was even greater than that of the plasmid containing 3.4 kb DNA originated from $\underline{E.}$ $\underline{coli}$ chromosome.
This implies that the unidentified DNA segment increases the frequency of recombination between the plasmid and the chromosome probably due to the presence of DNA sequence homologous to the chromosome. It is likely that the segment is a previously unidentified insertion sequence translocated from the chromosome of $\underline{E.}$ $\underline{coli}$ by illegitimate recombination. The identity of the segment remains to be discovered.
대장균의 conduction 과정을 이용하여 염색체내에 있는 특정 유전자의 돌연변이를 플라스미드로 옮기는 새로운 방법을 시도하던중 그 크기가 약 1.5 kb 정도 되는 DNA 조각을 발견하였다.
이 DNA 조각의 제한효소 지도를 만든 결과 Bgl II 와 Hind III 자리가 있는것으로 나타났다. 또한 염색체로 상동성 재조합에 의해 삽입되는 빈도가 이 DNA 조각을 갖지 않은 다른 플라스미드에 비해서 약 10000배 정도 높은 것으로 나타났다. 이 DNA 조각과 염색체사이에 상동성 재조합이 일어난다는 것은 이것의 원래 위치는 염색체인데 플라스미드로 전위되어 온것을 의미한다.
