04-29-2008, 09:22 PM
23. Which of the following statements describing restriction endonucle¬ases is true?
a. They always yield overhanging single-stranded ends
b. They recognize methylated DNA sequences
c. They recognize triplet repeats
d. They cleave both strands in duplex DNA
e. They always yield blunt ends
24. DNA fingerprinting is used for paternity testing and forensic identifi¬cation of suspects. Which of the following is the most accurate description of DNA fingerprinting?
a. DNA can be isolated from blood, skin, or sperm and analyzed for variable pat¬terns of restriction fragments arising from tandemly repeated sequences (microsatellites)
b. DNA is copied from blood, skin, or sperm RNA using reverse transcriptase and analyzed for the pattern of complementary DNAs
c. DNA is isolated from blood, skin, or sperm and its fragment size distribution is analyzed by gel electrophoresis
d. DNA is isolated from blood, skin, or sperm and hybridized with probes from the HLA locus to visualize HLA gene patterns
e. DNA is isolated from blood, skin, or sperm, centrifuged to separate satellite DNA fractions, and analyzed by gel electrophoresis
25. The first drug to be effective against AIDS, including the reduction of maternal-to-child AIDS transmission by 30%, was AIDS drug azidothymi¬dine (AZT). Which of the following describes its mechanism of action?
a. It inhibits viral protein synthesis
b. It inhibits RNA synthesis
c. It inhibits viral DNA polymerase
d. It stimulates DNA provirus production
e. It inhibits viral reverse transcriptase
a. They always yield overhanging single-stranded ends
b. They recognize methylated DNA sequences
c. They recognize triplet repeats
d. They cleave both strands in duplex DNA
e. They always yield blunt ends
24. DNA fingerprinting is used for paternity testing and forensic identifi¬cation of suspects. Which of the following is the most accurate description of DNA fingerprinting?
a. DNA can be isolated from blood, skin, or sperm and analyzed for variable pat¬terns of restriction fragments arising from tandemly repeated sequences (microsatellites)
b. DNA is copied from blood, skin, or sperm RNA using reverse transcriptase and analyzed for the pattern of complementary DNAs
c. DNA is isolated from blood, skin, or sperm and its fragment size distribution is analyzed by gel electrophoresis
d. DNA is isolated from blood, skin, or sperm and hybridized with probes from the HLA locus to visualize HLA gene patterns
e. DNA is isolated from blood, skin, or sperm, centrifuged to separate satellite DNA fractions, and analyzed by gel electrophoresis
25. The first drug to be effective against AIDS, including the reduction of maternal-to-child AIDS transmission by 30%, was AIDS drug azidothymi¬dine (AZT). Which of the following describes its mechanism of action?
a. It inhibits viral protein synthesis
b. It inhibits RNA synthesis
c. It inhibits viral DNA polymerase
d. It stimulates DNA provirus production
e. It inhibits viral reverse transcriptase