![]() Two DNA double helices are formed, showing semi- conservative replication. RNA primer replaced with DNA by DNA polymerase I and finally, DNA fragments are connected by DNA ligase. DNA polymerase III adds complementary bases discontinuously in the 5’ to 3’ direction, forming Okazaki fragments. Primase adds a short RNA segment to the lagging stand. DNA polymerase III adds complementary bases continuously in the 5’ to 3’ direction ( leading strand ). Be sure to include the single- stranding binding proteins (SSBPs). Draw helicase as it begins to unwind the DNA at the replication fork. Draw the DNA double helix, with this sequence on the 5’ to 3’ strand: ACCGTATTGATC Label the 5’ and 3’ on each strand. Use the following link to help you, using the “Replication Fork” and “Fork with Proteins” links at the top of the page to help you. You must label all the bold words below in each drawing. You will use 3 different colors: one for the original strands of DNA, one for the leading strand, and one for the lagging strand. Which enzyme joins the Okazaki fragments together on the lagging strand? You will draw out the steps of the S-phase of Interphase, DNA replication. Which enzyme removes primers between Okazaki fragments? 28. ![]() What enzyme is responsible for unwinding the DNA double helix, allowing the polymerase to bind? 27. What is the difference between leading strands and lagging strands? 25. In what direction does DNA replication occur? 24. What is the role of DNA polymerase (III)? 22. Why is DNA replication called semi-conservative? 21. How does this allow DNA to duplicate itself (replicate)? 20. DNA replication happens only in the _ to _ direction. What are the discontinuously copied strands of the new DNA called? 17. IMG3675.jpg - 1 / 1 pts Question 5 Which strand is produced more rapidly Okazaki fragment Lagging strand Leading strand 3 0 5 Good. What enzyme synthesizes the new DNA strand? 16. Okazaki fragment Lagging strand Leading strand 3 0 5 Good. What enzyme unzips the parent strand of DNA? 15. What is the importance of DNA polymerase I? 14. When the replication fork reaches the end of the chromosome, however, there is (in many species, including humans) a short stretch of DNA that does not get covered by an Okazaki fragmentessentially, there's no way to get the fragment started because the primer would fall beyond the chromosome end 1 1 1 start superscript, 1, end superscript. What is a mutation? What would a mutation look like in a DNA molecule? 13. Create a matching (complementary) DNA sequence for the following strand: DNA Replication 10. How do eukaryotes speed the process of replication – since they have multiple long chromosomes? Part Three: Questions 9 – 25 DO NOT necessarily come from the links you used above but many will. How are Okazaki fragments on the lagging strand joined into one continuous strand? 8. Draw a picture of the replication fork and label all the components. Animation Two: DNA replication fork (Animation) 6. Explain elongation stage of replication – you answer should include a discussion of leading strand, lagging strand, Okazaki pieces and RNA primer. Why the two strands of the helix have to be elongated by two slightly different mechanisms? 5. Which enzyme is the key player in Replication? What is this enzyme’s limitation? How is this limitation overcome? 4. How does replication start? Who prevents the unwound DNA for twisting back? 3. ( is also a great link, click the “Fork with Proteins” link) 2. List the proteins/enzymes involved in the process of replication. Animation One: How Nucleotides are added in DNA replication? (Animation) 1. Nucleosomes are spaced at intervals of about 200 nucleotides pairs along the DNA strand, which may explain why new Okazaki fragments are synthesized on the lagging strand at intervals of 100-200 nucleotides in eukaryotes, instead of 1000-2000 nucleotides as in bacteria.Īs already discussed by me and in the comments, increasing telomere longevity in eukaryotes by reducing the length of okazaki fragments, and consequently reducing the part of telomere cut-off after every division might be another reason for having shorter fragments in eukaryotes as compared to prokaryotes which do not contain telomeres.ĮDIT : Having thought over it again, the relation between Okazaki fragment length and telomeres do not seem logical as only RNA primer length is important when considering telomere length.īalakrishnan and Bambara (2013) explain the regulation of (and differences between) prokaryotic and eukaryotic Okazaki fragments in detail.DNA Replication Worksheet Name: Directions: The students will use the two animations from the below link to answer the question set for each of the first two animations. I have found one more possible reason from Bruce Alberts' The Molecular Biology of the Cell: (Ch.
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