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In semiconservative model of DNA replication, two parental strands unwind and are used for the synthesis of new strands, following the rule of complementary base pairing. The synthesis of the complementary strand requires that DNA synthesis proceed in the opposite direction, while the double helix is progressively unwinding and replicating in only one direction. One of the DNA strands is continuously synthesized in the same direction as the advancing replication fork and is called the leading strand, whereas the other strand is synthesized infrequently and is called the lagging strand. These short fragments are called as Okazaki fragments. These Okazaki fragments need to be matured in to continuous DNA strand by which of the following enzyme combinations?
- a)DNA pol III and DNA ligase
- b)DNA pol I and DNA ligase
- c)DNA pol II and DNA ligase
- d)DNA gyrase and DNA ligase
Correct answer is option 'B'. Can you explain this answer?
Verified Answer
In semiconservative model of DNA replication, two parental strands unw...
Concept:
- Cellular DNA replication requires efficient copying of the double-stranded chromosomal DNA.
- The leading strand is elongated continuously in the direction of fork opening, whereas the lagging strand is made discontinuously in the opposite direction.
- The lagging strand needs to be processed to form a functional DNA segment.
- Genetic analyses and reconstitution experiments identified proteins and multiple pathways responsible for maturation of the lagging strand.
- In both prokaryotes and eukaryotes the lagging-strand fragments are initiated by RNA primers, which are removed by a joining mechanism involving strand displacement of the primer into a flap, flap removal, and then ligation.
- Although the prokaryotic fragments are ∼1200 nucleotides long, the eukaryotic fragments are much shorter, with lengths determined by nucleosome periodicity.
- The prokaryotic joining mechanism is simple and efficient. The eukaryotic maturation mechanism involves many enzymes, possibly three pathways, and regulation that can shift from high efficiency to high fidelity.
Explanation:
- Because DNA polymerases cannot incorporate dNTPs without a primer terminated by a 3′ hydroxyl, the leading strand and each Okazaki fragment are primed by RNA to initiate synthesis .
- On the lagging strand the primer is extended by the addition of dNMPs to form short segments of DNA.
- These segments need to be further processed to form a fully functional strand of DNA.
- Specifically, the RNA primers have to be excised from the fragments.
- Removal of RNA primers is performed partly by a ribonuclease H (RNase H).
- In eukaryotes, the initiator RNA primers are removed, apparently by two partly redundant processes.
- The first is the action of cellular RNase H2, which can begin degrading the primer as soon as it is made, but presumably not so soon that it interferes with initiation of DNA synthesis.
- RNase H2 degrades between ribonucleotides of an RNA strand annealed to DNA. It cannot cleave between the 3′-most ribonucleotide and the initial deoxynucleotide.
- A second nuclease is needed for this.
- The second nuclease operates after strand displacement synthesis resulting from extension of the 3′ end of the adjacent fragment.
- This synthesis raises what remains of the RNA primer into a single-stranded flap structure that is removed by endonuclease action. The resulting nick is then ligated by DNA ligase to make a continuous strand.
- Fundamental differences among organisms include structural variations in the proteins involved, and length variations in the fragments.
- DNA polymerase I (pol I) processes RNA primers during lagging-strand synthesis and fills small gaps during DNA repair reactions.
- However, it is unclear how pol I and pol III work together during replication and repair or how extensive pol I processing of Okazaki fragments is in vivo.
hence the correct answer is option 1
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In semiconservative model of DNA replication, two parental strands unwind and are used for the synthesis of new strands, following the rule of complementary base pairing. The synthesis of the complementary strand requires that DNA synthesis proceed in the opposite direction, while the double helix is progressively unwinding and replicating in only one direction. One of the DNA strands is continuously synthesized in the same direction as the advancing replication fork and is called the leading strand, whereas the other strand is synthesized infrequently and is called the lagging strand. These short fragments are called as Okazaki fragments. These Okazaki fragments need to be matured in to continuous DNA strand by which of the following enzyme combinations?a)DNA pol III and DNA ligaseb)DNA pol I and DNA ligasec)DNA pol II and DNA ligased)DNA gyrase and DNA ligaseCorrect answer is option 'B'. Can you explain this answer?
Question Description
In semiconservative model of DNA replication, two parental strands unwind and are used for the synthesis of new strands, following the rule of complementary base pairing. The synthesis of the complementary strand requires that DNA synthesis proceed in the opposite direction, while the double helix is progressively unwinding and replicating in only one direction. One of the DNA strands is continuously synthesized in the same direction as the advancing replication fork and is called the leading strand, whereas the other strand is synthesized infrequently and is called the lagging strand. These short fragments are called as Okazaki fragments. These Okazaki fragments need to be matured in to continuous DNA strand by which of the following enzyme combinations?a)DNA pol III and DNA ligaseb)DNA pol I and DNA ligasec)DNA pol II and DNA ligased)DNA gyrase and DNA ligaseCorrect answer is option 'B'. Can you explain this answer? for Software Development 2025 is part of Software Development preparation. The Question and answers have been prepared according to the Software Development exam syllabus. Information about In semiconservative model of DNA replication, two parental strands unwind and are used for the synthesis of new strands, following the rule of complementary base pairing. The synthesis of the complementary strand requires that DNA synthesis proceed in the opposite direction, while the double helix is progressively unwinding and replicating in only one direction. One of the DNA strands is continuously synthesized in the same direction as the advancing replication fork and is called the leading strand, whereas the other strand is synthesized infrequently and is called the lagging strand. These short fragments are called as Okazaki fragments. These Okazaki fragments need to be matured in to continuous DNA strand by which of the following enzyme combinations?a)DNA pol III and DNA ligaseb)DNA pol I and DNA ligasec)DNA pol II and DNA ligased)DNA gyrase and DNA ligaseCorrect answer is option 'B'. Can you explain this answer? covers all topics & solutions for Software Development 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for In semiconservative model of DNA replication, two parental strands unwind and are used for the synthesis of new strands, following the rule of complementary base pairing. The synthesis of the complementary strand requires that DNA synthesis proceed in the opposite direction, while the double helix is progressively unwinding and replicating in only one direction. One of the DNA strands is continuously synthesized in the same direction as the advancing replication fork and is called the leading strand, whereas the other strand is synthesized infrequently and is called the lagging strand. These short fragments are called as Okazaki fragments. These Okazaki fragments need to be matured in to continuous DNA strand by which of the following enzyme combinations?a)DNA pol III and DNA ligaseb)DNA pol I and DNA ligasec)DNA pol II and DNA ligased)DNA gyrase and DNA ligaseCorrect answer is option 'B'. Can you explain this answer?.
In semiconservative model of DNA replication, two parental strands unwind and are used for the synthesis of new strands, following the rule of complementary base pairing. The synthesis of the complementary strand requires that DNA synthesis proceed in the opposite direction, while the double helix is progressively unwinding and replicating in only one direction. One of the DNA strands is continuously synthesized in the same direction as the advancing replication fork and is called the leading strand, whereas the other strand is synthesized infrequently and is called the lagging strand. These short fragments are called as Okazaki fragments. These Okazaki fragments need to be matured in to continuous DNA strand by which of the following enzyme combinations?a)DNA pol III and DNA ligaseb)DNA pol I and DNA ligasec)DNA pol II and DNA ligased)DNA gyrase and DNA ligaseCorrect answer is option 'B'. Can you explain this answer? for Software Development 2025 is part of Software Development preparation. The Question and answers have been prepared according to the Software Development exam syllabus. Information about In semiconservative model of DNA replication, two parental strands unwind and are used for the synthesis of new strands, following the rule of complementary base pairing. The synthesis of the complementary strand requires that DNA synthesis proceed in the opposite direction, while the double helix is progressively unwinding and replicating in only one direction. One of the DNA strands is continuously synthesized in the same direction as the advancing replication fork and is called the leading strand, whereas the other strand is synthesized infrequently and is called the lagging strand. These short fragments are called as Okazaki fragments. These Okazaki fragments need to be matured in to continuous DNA strand by which of the following enzyme combinations?a)DNA pol III and DNA ligaseb)DNA pol I and DNA ligasec)DNA pol II and DNA ligased)DNA gyrase and DNA ligaseCorrect answer is option 'B'. Can you explain this answer? covers all topics & solutions for Software Development 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for In semiconservative model of DNA replication, two parental strands unwind and are used for the synthesis of new strands, following the rule of complementary base pairing. The synthesis of the complementary strand requires that DNA synthesis proceed in the opposite direction, while the double helix is progressively unwinding and replicating in only one direction. One of the DNA strands is continuously synthesized in the same direction as the advancing replication fork and is called the leading strand, whereas the other strand is synthesized infrequently and is called the lagging strand. These short fragments are called as Okazaki fragments. These Okazaki fragments need to be matured in to continuous DNA strand by which of the following enzyme combinations?a)DNA pol III and DNA ligaseb)DNA pol I and DNA ligasec)DNA pol II and DNA ligased)DNA gyrase and DNA ligaseCorrect answer is option 'B'. Can you explain this answer?.
Solutions for In semiconservative model of DNA replication, two parental strands unwind and are used for the synthesis of new strands, following the rule of complementary base pairing. The synthesis of the complementary strand requires that DNA synthesis proceed in the opposite direction, while the double helix is progressively unwinding and replicating in only one direction. One of the DNA strands is continuously synthesized in the same direction as the advancing replication fork and is called the leading strand, whereas the other strand is synthesized infrequently and is called the lagging strand. These short fragments are called as Okazaki fragments. These Okazaki fragments need to be matured in to continuous DNA strand by which of the following enzyme combinations?a)DNA pol III and DNA ligaseb)DNA pol I and DNA ligasec)DNA pol II and DNA ligased)DNA gyrase and DNA ligaseCorrect answer is option 'B'. Can you explain this answer? in English & in Hindi are available as part of our courses for Software Development.
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