05-12-2008, 08:35 AM
need answers for these Qs plz
Q1
Bacterial strain X is resistant to ampicillin and sensitive to kanamycin. Bacterial strain Y is resistant to kanamycin and sensitive to ampicillin. Bacterial strains X and Y are grown in mixed culture in medium without antibiotics, then the culture is plated on medium containing both ampicillin and kanamycin. Bacterial colonies grow on the plates. In a second experiment, DNase is added to the mixed culture medium. When this mixed culture is plated on medium containing both antibiotics, no colonies grow. Assuming that bacterial cells are impermeable to DNase, which of the following processes best explains these observations?
A ) Conjugation
B ) Mutation
C ) Transduction
D ) Transformation
E ) Transposition
Q2
An 18-year-old woman who has hepatocellular carcinoma is treated with a new chemotherapeutic agent. One week after initiation of therapy, examination of tissue obtained on biopsy of the liver shows that many neoplastic cells have decreased in size. Many fragments of membrane-bound structures containing condensed nuclear chromatin and organelles are identified. Electrophoresis on agarose gel of DNA isolated from this tissue shows a "ladder" consisting of multiple regularly spaced DNA bands. Activation of which of the following enzymes is most likely to be responsible for the alterations in DNA?
A ) DNA ligase
B ) DNA polymerase
C ) Endonuclease
D ) Phospholipase A2
E ) Transglutaminase
Q1
Bacterial strain X is resistant to ampicillin and sensitive to kanamycin. Bacterial strain Y is resistant to kanamycin and sensitive to ampicillin. Bacterial strains X and Y are grown in mixed culture in medium without antibiotics, then the culture is plated on medium containing both ampicillin and kanamycin. Bacterial colonies grow on the plates. In a second experiment, DNase is added to the mixed culture medium. When this mixed culture is plated on medium containing both antibiotics, no colonies grow. Assuming that bacterial cells are impermeable to DNase, which of the following processes best explains these observations?
A ) Conjugation
B ) Mutation
C ) Transduction
D ) Transformation
E ) Transposition
Q2
An 18-year-old woman who has hepatocellular carcinoma is treated with a new chemotherapeutic agent. One week after initiation of therapy, examination of tissue obtained on biopsy of the liver shows that many neoplastic cells have decreased in size. Many fragments of membrane-bound structures containing condensed nuclear chromatin and organelles are identified. Electrophoresis on agarose gel of DNA isolated from this tissue shows a "ladder" consisting of multiple regularly spaced DNA bands. Activation of which of the following enzymes is most likely to be responsible for the alterations in DNA?
A ) DNA ligase
B ) DNA polymerase
C ) Endonuclease
D ) Phospholipase A2
E ) Transglutaminase