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Chapter 14: Problem 20

Which enzyme is most directly responsible for the main process of producing a new DNA strand? a. DNA pol I b. DNA pol II c. DNA pol III d. DNA pol I, DNA pol II, and DNA pol III

Short Answer

Expert verified
DNA pol III

Step by step solution

01

鈥� Understand the Role of Each Enzyme

Firstly, identify the roles of DNA polymerase enzymes. DNA polymerase I is involved mainly in DNA repair and removing RNA primers. DNA polymerase II also plays a role in DNA repair mechanisms. DNA polymerase III is primarily responsible for the synthesis of the new DNA strand during replication.
02

鈥� Analyze the Main Process

The main process in question is the synthesis of a new DNA strand. During DNA replication, the enzyme tasked with synthesizing the new strand by adding nucleotides in the 5' to 3' direction is crucial.
03

鈥� Match the Correct Enzyme

Match the enzyme most directly responsible for the synthesis of the new DNA strand. Given that DNA polymerase III is responsible for the elongation of the new DNA strand during replication, it is the correct choice.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

DNA polymerase III
DNA polymerase III is a key enzyme in DNA replication. Its main job is to add nucleotides to the new DNA strand, making it longer one base at a time. This process happens at an incredibly high speed, ensuring that the DNA replication is quick and efficient. Unlike other DNA polymerases, DNA polymerase III is specialized for accuracy and speed. It has a proofreading ability to correct mistakes during replication. If an incorrect nucleotide is added, the enzyme can remove it and replace it with the correct one. This prevents mutations and ensures the integrity of the genetic information being copied.
DNA strand synthesis
DNA strand synthesis is a critical part of the overall DNA replication process. During DNA replication, the double helix unwinds, creating two template strands. Each template serves as a guide for the synthesis of a new complementary strand. DNA polymerase III attaches to the original strand and begins to add complementary nucleotides. For example, if the original strand has a cytosine (C), DNA polymerase III will add a guanine (G) to the new strand. This new strand is built in the 5' to 3' direction. This means the enzyme can only add new nucleotides to the 3' end of the growing strand. This directional synthesis is a defining characteristic of DNA replication.
DNA replication process
DNA replication is the method by which a cell duplicates its DNA before it divides. The process starts at specific locations on the DNA molecule called origins of replication. Here鈥檚 a brief overview of the steps involved:
  • The DNA double helix unwinds, and the two strands separate.
  • Each strand serves as a template for the formation of a new complementary strand.
  • Primase synthesizes a short RNA primer that provides a starting point for DNA polymerase III.
  • DNA polymerase III then adds nucleotides to the RNA primer, extending the new DNA strand.
  • On one template strand, DNA synthesis proceeds continuously in the direction of the replication fork (leading strand synthesis). On the other strand, it is discontinuous, forming short fragments called Okazaki fragments (lagging strand synthesis).
  • Later, other enzymes like DNA polymerase I replace the RNA primers with DNA nucleotides, and DNA ligase seals any gaps between the fragments.
By the end of replication, two identical DNA molecules are formed. This ensures that each new cell will have an exact copy of the DNA. The coordination of all these steps ensures that DNA replication is highly accurate and efficient.

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Most popular questions from this chapter

During proofreading, which of the following enzymes reads the DNA? a. DNA polymerase b. helicase c. topoisomerase d. primase

Explain the events taking place at the replication fork. If the gene for helicase is mutated, what part of replication will be affected? a. Helicase separates the DNA strands at the origin of replication. Topoisomerase breaks and reforms DNA鈥檚 phosphate backbone ahead of the replication fork, thereby relieving the pressure. Single-stranded binding proteins prevent reforming of DNA. Primase synthesizes RNA primer which is used by DNA polymerase to form a daughter strand. If helicase is mutated, the DNA strands will not be separated at the beginning of replication. b. Helicase joins the DNA strands together at the origin of replication. Topoisomerase breaks and reforms DNA鈥檚 phosphate backbone after the replication fork, thereby relieving the pressure. Single-stranded binding proteins prevent reforming of DNA. Primase synthesizes RNA primer which is used by DNA polymerase to form a daughter strand. If helicase is mutated, the DNA strands will not be joined together at the beginning of replication. c. Helicase separates the DNA strands at the origin of replication. Topoisomerase breaks and reforms DNA鈥檚 sugar backbone ahead of the replication fork, thereby increasing the pressure. Single-stranded binding proteins prevent reforming of DNA. Primase synthesizes DNA primer which is used by DNA polymerase to form a daughter strand. If helicase is mutated, the DNA strands will be separated at the beginning of replication. d. Helicase separates the DNA strands at the origin of replication. Topoisomerase breaks and reforms DNA鈥檚 sugar backbone ahead of the replication fork, thereby relieving the pressure. Single-stranded binding proteins prevent reforming of DNA. Primase synthesizes DNA primer which is used by RNA polymerase to form a parent strand. If helicase is mutated, the DNA strands will be separated at the beginning of replication.

Compare and contrast the roles of DNA polymerase I and DNA ligase in DNA replication. a. DNA polymerase I removes the RNA primers from the developing copy of DNA. DNA ligase seals the ends of the new segment, especially the Okazaki fragments. b. DNA polymerase I adds the RNA primers to the already developing copy of DNA. DNA ligase separates the ends of the new segment, especially the Okazaki fragments. c. DNA polymerase I seals the ends of the new segment, especially the Okazaki fragments. DNA ligase removes the RNA primers from the developing copy of DNA. d. DNA polymerase I removes the enzyme primase from the developing copy of DNA. DNA ligase seals the ends of the old segment, especially the Okazaki fragments.

What prevents the further development of a DNA strand in Sanger sequencing? a. the addition of DNA reductase b. the addition of dideoxynucleotides c. the elimination of DNA polymerase d. the addition of uracil

What can be the result of DNA failing to undergo repair after too much UV exposure? a. second degree burns b. a malignant melanoma c. a breakdown of deep layers of the skin d. a sun burn
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