Question

1) A plasmid has the antibiotic resistance genes for kanamycin and ampicillin. You insert foreign DNA into the ampicillin resistance gene. E. coli containing the recombinant plasmid (plasmid + foreign DNA) will grow in the presence of ampicillin but not in the presence of kanamycin.

A)True

B)False

2)Expression of a gene could result in...

A) transcription of a mRNA from the gene

B) transcription of a protein from the gene

C) translation of the DNA of the gene

3)Restriction enzymes like EcoRI are endonucleases. An endonuclease will...

A) Break glycosidic bonds

B) Break a phosphodiester bond only at the 3' or 5' end of DNA

C) Break a phosphodiester bond in the interior of a polynucleotide but not at the ends.

Answer 1

1) Antibiotics are substances that kill or inhibit the growth of bacteria. Antibiotic resistance means that there are certain changes in the bacteria which allows them to grow even in presence of antibiotics .Now, as per the question intitially,the plasmid has gene that is resistant for ampicillin and kanamycin.later , on insertion of foreign DNA in ampicillin resistant Gene, Ecoli. Will continue to grow in presence of kanamycin but will loose the capability of gene to grow in presence of ampicillin, as the site is blocked by foreign DNA. Therefore, the statement is false (B).

2)Expression of gene results in the formation of product like protein or RNA.The process involved in the formation of RNA from a gene( strand of DNA) is called transcription , therefore option (A) is correct.

3) Restriction enzymes are know to have the cleavage property of DNA at given specific sites.Now one of them is endonuclease.As the name suggests , it is known to break the phosphodiester bonds in the interior(Endo) of a polynucleotide but not at the ends.Therefore option (C) is correct.