3/21/2023 0 Comments Okazaki fragments![]() ![]() The 3' end has a hydroxyl (-OH) group on the deoxyribose sugar, whereas the 5' end has a phosphate group. The DNA double helix is constructed from two strands of DNA, each with a sugar-phosphate backbone and nitrogenous bases that form hydrogen bonds, holding the two strands together. Labels can be used once, more than once, or not at all. Use only the pink labels for the pink targets, and the blue labels for the blue targets. The structure and orientation of the two strands are important to understanding DNA replication.ĭrag the labels to their appropriate locations on the diagram below. Each nucleotide consists of a sugar, a phosphate group, and one of four nitrogenous bases. The DNA double helix is composed of two strands of DNA each strand is a polymer of DNA nucleotides. Part A - The chemical structure of DNA and its nucleotides DNA Replication (1 of 2): DNA Structure and Replication Machinery (BioFlix tutorial) This statement correctly describes the conditions of DNA replication. Which of the following statements about DNA replication is true? DNA synthesis is continuous on the leading strand and discontinuous on the lagging strand. Okazaki fragments are short sequences synthesized in the lagging strand because DNA polymerase can synthesize only from 5' to 3' and the DNA strands are antiparallel. Which of the following statements is true regarding Okazaki fragments? They are short fragments of DNA synthesized from RNA primers on the lagging strand. Gyrase relieves the tension by forming negative supercoils in a reaction that requires energy from the hydrolysis of ATP. coli is responsible for relieving the tension ahead of the fork that results when the DNA unwinds to form the replication "bubble" or "eye"? DNA gyrase An endonuclease is involved in removing bases sequentially from one end of DNA or the other. During replication, primase adds a DNA primer to RNA. DNA strand replication begins with an RNA primer. If the wrong nucleotide is inserted, normal base pairing will not be observed and the base in error will be removed from the newly synthesized strand before subsequent nucleotides are added. coli DNA polymerase I is responsible for proofreading the newly synthesized DNA? 3' to 5' exonuclease the 5′ to 3′ polarity restriction DNA replication occurs in the 5′ to 3′ direction that is, new nucleoside triphosphates are added to the 3′ end. The discontinuous aspect of replication of DNA in vivo is caused by _. The template strand is complementary and antiparallel to the sequenced strand: 5'-CAACTGGTCCAT-3', in this example. Therefore, the 5' to 3' sequence of nucleotides in the sequenced strand can be determined by reading the bands in all lanes from the bottom of the gel to the top: 5'-ATGGACCAGTTG-3', in this example. That fragment represents the 5' nucleotide of the sequenced strand. The shortest fragment generated by the dideoxynucleotide DNA sequencing reaction migrates to the bottom of the gel. Use only capital letters for the sequence. Type the 5' to 3' sequence of the template strand ("inferred strand") based on the pattern in this gel. The diagram below shows an autoradiograph of a DNA sequencing gel. Part C - Dideoxynucleotide DNA sequencing On the lagging strand, DNA ligase joins Okazaki fragments by forming phosphodiester bonds between them, thus completing DNA replication. DNA polymerase I removes the RNA primers and replaces them with DNA nucleotides. Primase creates short RNA primers, initiating DNA synthesis on both template strands. DNA polymerase III synthesizes the new strands, but it requires an existing 3′ hydroxyl (-OH) group to add nucleotides. Single-stranded binding proteins bind to the single strands of DNA, preventing them from reannealing and allowing synthesis to occur on both strands. Several proteins are involved in DNA replication, including the following: Helicase breaks the hydrogen bonds between the parental DNA strands and unwinds the double helix. On the other template strand, DNA is synthesized away from the replication fork in segments called Okazaki fragments, generating the lagging strand. On one template strand, synthesis proceeds continuously toward the replication fork, generating the leading strand. uring replication, DNA synthesis occurs in the 5′ to 3′ direction along both template strands. I) Synthesizes DNA 5' to 3' on leading and lagging strands. H) Coats single-stranded DNA, preventing duplex formation. E) lagging strand F) Leading Strand G) Relaxes supercoiled DNA. D) Catalyzes phosphodiester bond formation, joining DNA fragments. C) Replaces RNA primers with DNA nucleotides. B) Synthesizes RNA primers on leading and lagging strands. A) Breaks hydrogen bonds, unwinding DNA double helix.
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