26..............28 - ebnalfady

[ArchivalUser]

26. Which of the following enzymes can polymerize deoxyribonu¬cleotides into DNA?
a. Primase
b. DNA ligase
c. DNA gyrase
d. RNA polymerase III
e. Reverse transcriptase

27. Which of the following statements correctly describes the recombi¬nant DNA tool known as plasmids?
a. They are found more commonly in viruses than in bacteria
b. They are single-stranded circles
c. They sometimes enhance bacterial susceptibility to antibiotics
d. They sometimes enhance bacterial resistance to antibiotics
e. They are too small to be useful as vectors for the cloning of mammalian DNA segments

28. Which of the following molecules is found in a nucleoside?
a. A pyrophosphate group
b. A 1² base linked to a pentose sugar
c. A 5²-phosphate group linked to a pentose sugar
d. A 3²-phosphate group linked to a pentose sugar
e. A terminal triphosphate

[ArchivalUser]

26. e
27. d
28c

[ArchivalUser]

26. e
27. d
28c

[ArchivalUser]

26-e
27-d
28-c

[ArchivalUser]

ANY ONE OTHER WANT TO TRY BEFORE POSTING THE ANSWERS

[ArchivalUser]

they are all correct

[ArchivalUser]

a
d
c

[ArchivalUser]

E
D
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EXPLANATION OF FOR Q...NO ... 28

.) A nucleoside consists of a purine or pyrimidine base linked to a pentose sugar. The 1² carbon of the pentose is linked to the nitro¬gen of the base. In DNA, 2²-deoxyribose sugars are used; in RNA, ribose sugars are used. Nucleotides are phosphate esters of nucleosides with one to three phosphate groups, such as adenosine monophosphate (AMP), adeno¬sine diphosphate (ADP), or adenosine triphosphate (ATP). The nitrogenous bases are adenine, thymine, guanine, and cytosine in DNA, with thymine replaced by uridine in RNA. Nucleotide polymers are chains of nucleotides with single phosphate groups, joined by bonds between the 3²-hydroxyl of the preceding pentose and the 5²-phosphate of the next pentose. Polymer¬ization requires high-energy nucleotide triphosphate precursors that liber¬ate pyrophosphate (broken down to phosphate) during joining. The polymerization reaction is given specificity by complementary RNA or DNA templates and rapidity by enzyme catalysts called polymerases.