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Module 11 Lesson 2 Progress Check

Prompt

Read Lesson 2 and complete "Check Your Progress" questions #1-4 on p.298.

Response

  1. Indicate the sequence of the template strand if a nontemplate strand has the sequence 5' ATGGGGCGC 3'.

    The sequence of the template strand corresponding to the given non-template strand sequence 5' ATGGGGCGC 3' would be 3' TACCCGCGC 5'. This is because DNA strands are antiparallel and complementary, with adenine (A) pairing with thymine (T) and cytosine (C) pairing with guanine (G). The template strand is read in the 3' to 5' direction by DNA polymerase during replication.

  2. Describe the role of DNA helicase, DNA polymerase, and DNA ligase.

    DNA helicase unwinds the DNA double helix at the replication fork, allowing the strands to be copied. DNA polymerase synthesizes new DNA strands by adding nucleotides complementary to the template strand. DNA ligase joins Okazaki fragments on the lagging strand, ensuring a continuous double-stranded DNA molecule.

  3. Diagram the way leading and lagging strands are synthesized.

    In DNA replication, the leading strand is synthesized continuously towards the replication fork, while the lagging strand is synthesized in short, discontinuous segments known as Okazaki fragments. The synthesis directionality, dictated by DNA polymerase, requires the lagging strand to be synthesized in a series of steps that include laying down RNA primers, extending them, and then joining these fragments with DNA ligase. This results in one strand being easily and continuously replicated, and the other requiring more complex, step-wise synthesis.

  4. Explain why DNA replication is more complex in eukaryotes than in bacteria.

    DNA replication is more complex in eukaryotes due to their larger genomes and the presence of multiple origins of replication on each chromosome. Eukaryotic cells also have a tightly regulated cell cycle ensuring replication occurs only once per cycle, and their chromatin structure necessitates additional proteins for remodeling during replication. Additionally, the eukaryotic replication machinery is more complex, featuring a greater variety of DNA polymerases and associated factors compared to bacteria.