MCQ DNA REPLICATION PART-II

MCQ DNA REPLICATION PART-II 5-9-2011 1. The enzyme that (during replication) proceeds along one of the strands of a DNA molecule adding deoxy-nucleotide-triphosphates to hydrogen bond with their appropriate complementary dNTP on the other single strand and to form a covalent phosphodiester bond with the previous nucleotide of the same strand is called A) Primase B) DNA polymerse II C) DNA polymerase III D) DNA Polymerase I 2. DNA Polymerase III is actually an aggregate of several different protein subunits. So it is often called a Holoenzyme Primeosome Replisome None of the above 3. The enzyme that creates a short RNA oligonucleotide at initiation sites where replication is to be carried out is called Primase DNA ligase DNA gyrase Exonuclese 4. Because DNA polymerase III can only act from 5' to 3', continuous strand growth can be achieved only along one of the template strands (Leading strand) and strand growth along the other strand must occur discontinuously resulting in the production of a series of short sections of new DNA called Replicon fragments Okazaki fragments Klenow fragments None of the above 5. The enzyme X removes RNA primers attached by Primase and this gap is then filled in by DNA Polymerase I. The enzyme X is RNase H DNA amylase DNA ligase Reverse transcriptase 6. The enzyme responsible for initiating the unwinding of double-stranded DNA (eliminating supercoiling) by nicking a single strand of the DNA molecule is A) Gyrase B) Ligase C) Topoisomerase D) Helicase 7. The enzyme that accomplishes the unwinding of the original double stranded DNA molecule, once supercoiling has been eliminated, by breaking the hydrogen bonds that hold the two strands together is Topoisomerase Helicase DNA Polymerase II Primase 8. Major difference between DNA replication in prokaryotes and eukaryotes is prokaryotes do not use Topoisomerase in the replication process replication is conservative in prokaryotes DNA amylase performs the function of DNA helicase in prokaryotes there is only one replication origin in prokaryotes. 9. DNA polymerase III is thought to add nucleotides to the 5' end of the RNA primer to the 3' end of the RNA primer in the place of the primer RNA after it is removed on single stranded templates without need for an RNA primer 10. The presence of and ___ with a free 3'-OH group is essential for DNA polymerase to synthesize DNA since no known DNA polymerase is able to initiate chains. origin of replication restriction endonuclease palindrome primer 11. The RNA polymerase that produces the primer necessary for DNA synthesis is called the origin of replication primase ligase topoisomerase 12. DNA Replication is semi conservative was first experimentally proved by A. Taylor B. Watson and Crick C. Meselson and Stahl D. H G Khorana 13. Which of the following is true for DNA helicases ? A. Promotes separation of two parental strands and establish replication fork B. DNA helicase hydrolyses ATP C. DNA helicase are ATP dependent unwinding enzymes D. all of these 14. A DNA strand on which new DNA strand is synthesized is called A. Complementary B. Template C. Primer D. Okazaki fragment 15. In DNA Replication the Okazaki fragments on the lagging strand are joined together by A. DNA ligase B. DNA Polymerase C. DNA Helicase D. Primase