DNA Replication

1. Watch this video

2. Study this summary

DNA Replication: Key Concepts

  • During DNA replication, each strand of the double helix acts as a template for synthesizing a new complementary strand.
  • This process is semiconservative: each daughter DNA molecule has one conserved parent strand and one newly synthesized strand.

Big Picture: DNA Replication Overview

  • Semiconservative Replication:
    • Each daughter DNA molecule consists of:
      • One conserved strand from the parent molecule.
      • One newly synthesized strand.
    • Illustrated with color coding: parent strand (red) and new strand (orange).
  • Process:
    • Enzymes pull the double helix apart.
    • Each single strand acts as a template.
    • Free nucleotides in the nucleus pair with exposed bases following base-pairing rules:
      • A pairs with T, and C pairs with G.

Initiating DNA Replication

  • Origin of Replication: A specific sequence where replication begins.
  • Helicase:
    • Unzips the DNA by breaking hydrogen bonds between strands.
    • Creates a structure called a replication fork.

Key Enzymes and Their Roles

  1. DNA Polymerase:
    • Synthesizes new DNA strands by adding nucleotides to the 3′ end of a growing strand.
    • Requires a template strand to guide nucleotide addition.
    • Has a limitation: can only extend from an existing strand.
  2. Primase:
    • Lays down a short RNA primer to provide a starting point for DNA polymerase.
  3. Single-Strand Binding Proteins:
    • Prevent the DNA strands from re-winding after being separated by helicase.

Leading Strand vs. Lagging Strand

  • Leading Strand:
    • Synthesized continuously in the same direction as the replication fork opens.
  • Lagging Strand:
    • Synthesized discontinuously in the opposite direction of the fork.
    • Formed in short segments called Okazaki fragments.
    • Each fragment requires a new primer.

Completing DNA Replication

  • DNA Polymerase I:
    • Removes RNA primers and replaces them with DNA.
  • DNA Ligase:
    • Seals gaps between Okazaki fragments, forming continuous strands.

Summary of Key Enzymes

  • DNA replication involves multiple enzymes working together in a coordinated process:
    • Helicase unzips the DNA.
    • DNA Polymerase synthesizes new strands.
    • Primase lays down RNA primers.
    • Ligase seals gaps between fragments.
    • Single-Strand Binding Proteins prevent re-winding.
  • Leading and lagging strand synthesis differ due to the directionality of DNA polymerase.

3. Master these flashcards

[qdeck bold_text=”false” style=”width: 625px !important; min-height: 475px !important;” ]

[h]DNA Replication Flashcards

[q json=”true” yy=”4″ unit=”6.Gene_Expression_and_Regulation” dataset_id=”AP_Bio_Flashcards_2022|1925a55316110″ question_number=”211″ topic=”6.1-2.DNA_and_RNA,_DNA_Replication”] DNA replication is semiconservative. On a big-picture level, describe how semiconservative replication occurs (and what that term means).

[a] During DNA replication,  a team of enzymes, using each strand of the double helix as a template, synthesizes new daughter strands. As a result, each daughter DNA double helix consists of one conserved strand from the parent molecule and another strand that was synthesized anew, making the process semi-conservative.

[q]Describe the roles of DNA polymerase, helicase, and single-strand binding proteins in DNA replication.

[a]Helicase opens up helix at the origin of replication, creating a replication fork. DNA polymerase creates sugar-phosphate bonds between a new nucleotide at the 3′ end of a new strand, and an existing DNA strand, building a new daughter strand in the 5′ to 3′ direction. Single-strand binding proteins keep the double helix from rewinding as replication occurs.

 

[q]What is primase, and why is it needed?

[a]DNA polymerase III can attach new nucleotides to a growing strand, but it can’t add a new nucleotide if there’s nothing to attach to. In other words, DNA polymerase’s active site requires that there be an existing strand behind it in the 5′ direction, and the correct new nucleotide ahead of it (in the 3′ direction). As a result, DNA polymerase III can’t initiate replication. Instead, another enzyme called primase (I) adds a short RNA primer (H) consisting of several RNA nucleotides. This primer holds onto the template strand through hydrogen bonds. Once the primer is in place, DNA polymerase III can start the replication process.

[q json=”true” yy=”4″ unit=”6.Gene_Expression_and_Regulation” dataset_id=”AP_Bio_Flashcards_2022|191c9fa502910″ question_number=”212″ topic=”6.1-2.DNA_and_RNA,_DNA_Replication”] Describe how DNA replication starts. End with the binding of DNA polymerase. In your response, include the roles of the following: the origin of replication, replication fork, RNA primase, and primer.

[a] Replication begins when an enzyme called helicase (1) finds a sequence called the origin of replication and separates the double-stranded DNA, exposing two single strands in a structure called a replication fork (7). An enzyme called RNA primase (5) lays down a short stretch of complementary RNA called a primer (4). The primer enables DNA polymerase (2) to bind and to use the template strand (dark blue) as a guide for synthesizing a complementary strand (light blue), always adding new nucleotides at the 3’ end of a growing strand.

[q json=”true” yy=”4″ unit=”6.Gene_Expression_and_Regulation” dataset_id=”AP_Bio_Flashcards_2022|191374b630d10″ question_number=”213″ topic=”6.1-2.DNA_and_RNA,_DNA_Replication”] How is DNA replication at the leading strand different from replication at the lagging strand?

[a] In the leading strand (4), DNA replication is relatively continuous, as DNA polymerase (3) follows the opening replication fork. In the lagging strand, DNA polymerase synthesizes in the opposite direction from the opening replication fork. This results in short sequences that are called Okazaki fragments (5).

[q json=”true” yy=”4″ unit=”6.Gene_Expression_and_Regulation” dataset_id=”AP_Bio_Flashcards_2022|190a49c75f110″ question_number=”214″ topic=”6.1-2.DNA_and_RNA,_DNA_Replication”] Describe the roles of ligase and topoisomerase in DNA replication. 

[a] After DNA polymerase has laid down all of the complementary nucleotides that it can, an enzyme called ligase (N) creates a sugar-phosphate bond between DNA fragments. Throughout the replication process, enzymes called topoisomerases (not shown) nick DNA’s sugar-phosphate backbone, preventing the DNA from overwinding, and then resealing the break.

[q]What happens during DNA replication?
[a]Each strand of the double helix acts as a template for synthesizing a new complementary strand.

[q]What does semiconservative replication mean?
[a]Each daughter DNA molecule consists of one conserved parent strand and one newly synthesized strand.

[q]Which enzymes are involved in DNA replication, and what are their functions?
[a]- **Helicase**: Unzips the DNA.
– **DNA Polymerase**: Synthesizes new strands.
– **Primase**: Lays down RNA primers.
– **Ligase**: Seals gaps between fragments.
– **Single-Strand Binding Proteins**: Prevent re-winding of DNA strands.

[q]How do leading and lagging strands differ during DNA replication?
[a]- **Leading Strand**: Synthesized continuously in the same direction as the replication fork.
– **Lagging Strand**: Synthesized discontinuously in short segments (Okazaki fragments) in the opposite direction of the replication fork.

[q]What is semiconservative replication?
[a]It’s the method of DNA replication where each new DNA molecule contains one conserved parent strand and one newly synthesized strand.

[q]What is the origin of replication?
[a]A specific DNA sequence where replication begins.

[q]What is the function of helicase?
[a]Helicase unzips the DNA by breaking hydrogen bonds, creating a replication fork.

[q]What does DNA polymerase do?
[a]DNA polymerase synthesizes new DNA strands by adding nucleotides to the 3′ end of a growing strand, following base-pairing rules.

[q]Why does DNA polymerase need an RNA primer?
[a]DNA polymerase can only add nucleotides to an existing strand, so it requires an RNA primer to start the process.

[q]What role do single-strand binding proteins play in replication?
[a]They prevent the DNA strands from re-winding after helicase separates them.

[q]How is the lagging strand synthesized?
[a]The lagging strand is synthesized discontinuously in short Okazaki fragments, each requiring a primer.

[q]What is the function of DNA polymerase I?
[a]DNA polymerase I removes RNA primers and replaces them with DNA.

[q]What is the role of DNA ligase?
[a]DNA ligase seals gaps between Okazaki fragments, forming continuous DNA strands.

[/qdeck]

4. Tackle these quizzes

4.1. DNA Replication, the Big Picture

[qwiz random = “true”]

[h]DNA replication: The Big Picture

[i]

 

[q]Copying of DNA is more formally known as DNA [hangman].

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[q]During replication, each strand acts as a [hangman] for the synthesis of a new strand.

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[q]During DNA replication, the new nucleotides that bind with the template strands are [hangman] to the nucleotides on the template strands. These new nucleotides form [hangman] bonds with the template strand nucleotides.

[c]Y29tcGxlbWVudGFyeQ==[Qq]

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[q]Whereas the bonds between nitrogenous bases are [hangman] bonds, the bonds between the sugars and phosphates on adjacent nucleotides are [hangman] bonds.

[c]aHlkcm9nZW4=[Qq]

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[q]Replication ends as enzymes create covalent bonds between [hangman] and phosphates on adjacent nucleotides.

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[Qq]

[q]The result of replication is two daughter DNA molecules, each of which has one [hangman] strand and one old strand.

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[q]Because replication results in daughter strands that are half new and half old, replication is called [hangman]-[hangman].

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[/qwiz]

 

4.2. DNA Replication in Cells

[qwiz random=”true” style=”width: 550px !important; min-height: 400px !important;” ]

[h]DNA Replication in Cells

[i]


[q]Which of the enzymes below is responsible for separating DNA into single strands so that each strand can be replicated?
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[q]Which of the enzymes below is responsible for replacing the RNA primer with DNA nucleotides?
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[c]RE5BIHBvbHltZXJhc2UgSUlJ[Qq]
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[c]c2luZ2xlIHN0cmFuZCBiaW5kaW5nIHByb3RlaW5z[Qq]
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[q]Which of the enzymes below is the one that creates sugar-phosphate bonds connecting adjacent DNA fragments?
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[c]RE5BIHBvbHltZXJhc2UgSUlJ[Qq]
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[q]Which of the enzymes below is the one that lays down a short primer of RNA, allowing DNA polymerase III to start attaching new DNA nucleotides to the growing strand?
[c]RE5BIHBvbHltZXJhc2UgSQ==[Qq]
[c]RE5BIHBvbHltZXJhc2UgSUlJ[Qq]
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[c]bGlnYXNl[Qq]
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[c]c2luZ2xlLXN0cmFuZCBiaW5kaW5nIHByb3RlaW5z[Qq]
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[q]Which of the molecules below bind to the exposed DNA strands and prevent them from rebinding to one another?
[c]RE5BIHBvbHltZXJhc2UgSQ==[Qq]
[c]RE5BIHBvbHltZXJhc2UgSUlJ[Qq]
[c]aGVsaWNhc2U=[Qq]
[c]bGlnYXNl[Qq]
[c]cHJpbWFzZQ==[Qq]
[c]c2luZ2xlLXN0cmFuZCBi aW5kaW5nIHByb3RlaW5z[Qq]
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Cg==[Qq]
[q]In the diagram below, which letter is helicase?

[textentry single_char=”true”]
[c]Qg ==[Qq]
[f]IFllcy4g4oCcQuKAnSBpcyBoZWxpY2FzZS4=[Qq]
[c]Kg==[Qq]
[f]Tm8uIEhlcmUmIzgyMTc7cyBhIGhpbnQuIEhlbGljYXNlIGlzIHRoZSBlbnp5bWUgdGhhdCBvcGVucyB1cCB0aGUgaGVsaXguIE9mIHRoZSBsZXR0ZXJlZCBpdGVtcyBpbiB0aGlzIGRpYWdyYW0sIHdoaWNoIGlzIHRoZSBvbmx5IG9uZSB0aGF0IGNvdWxkIGJlIGRvaW5nIHRoYXQ/[Qq]

[q]In the diagram below, which letter shows the origin of replication?

[textentry single_char=”true”]
[c]QQ ==[Qq]
[f]IFllcy4g4oCcQeKAnSBpcyB0aGUgb3JpZ2luIG9mIHJlcGxpY2F0aW9uLg==[Qq]
[c]Kg==[Qq]
[f]Tm8uIEhlcmUmIzgyMTc7cyBhIGhpbnQuIExvb2sgYXQgdGhlIGRpYWdyYW0gYmVsb3cuIFRoZSBvcmlnaW4gaXMgd2hlcmUgcmVwbGljYXRpb24gc3RhcnRzLiBOZXh0IHRpbWUgeW91IHNlZSB0aGlzIHF1ZXN0aW9uLCBhcHBseSB3aGF0JiM4MjE3O3Mgb2J2aW91c2x5IHRoZSBvcmlnaW4gaW4gdGhlIGRpYWdyYW0gYmVsb3cgdG8gdGhlIGRpYWdyYW0gYWJvdmUu[Qq]


[q]In the diagram below, which letter indicates a replication fork?

[textentry single_char=”true”]
[c]RQ ==[Qq]
[f]IFllcy4g4oCcReKAnSBpcyBhIHJlcGxpY2F0aW9uIGZvcmsu[Qq]
[c]Kg==[Qq]
[f]Tm8uIEhlcmUmIzgyMTc7cyBhIGhpbnQuIFRoZSByZXBsaWNhdGlvbiBmb3JrIGlzIHdoZXJlIHRoZSBzaW5nbGUgRE5BIHN0cmFuZCBpcyBzcGxpdCBvcGVuIGludG8gdHdvIHRlbXBsYXRlIHN0cmFuZHMuIFdpdGggdGhhdCBpbiBtaW5kLCB3aGF0IGFyZSB0aGUgb25seSBsZXR0ZXJzIGluIHRoaXMgZGlhZ3JhbSB0aGF0IGNvdWxkIHJlcHJlc2VudCBzb21ldGhpbmcgdGhhdCYjODIxNztzIGxpa2UgYSBmb3JrPw==[Qq]

[q]In the diagram below, which number indicates a replication fork?

[textentry single_char=”true”]
[c]Nw ==[Qq]
[f]IFllcy4g4oCcN+KAnSBpcyBhIHJlcGxpY2F0aW9uIGZvcmsu[Qq]
[c]Kg==[Qq]
[f]Tm8uIEhlcmUmIzgyMTc7cyBhIGhpbnQuIFRoZSByZXBsaWNhdGlvbiBmb3JrIGlzIHdoZXJlIHRoZSBzaW5nbGUgRE5BIHN0cmFuZCBpcyBzcGxpdCBvcGVuIGludG8gdHdvIHRlbXBsYXRlIHN0cmFuZHMuIFdpdGggdGhhdCBpbiBtaW5kLCB3aGF0IGlzIHRoZSBvbmx5IG51bWJlciBpbiB0aGlzIGRpYWdyYW0gdGhhdCBjb3VsZCByZXByZXNlbnQgc29tZXRoaW5nIHRoYXQmIzgyMTc7cyBsaWtlIGEgZm9yaz8=[Qq]

[q]In the diagram below, which number indicates helicase?

[textentry single_char=”true”]
[c]MQ ==[Qq]
[f]IFllcy4g4oCcMeKAnSBpcyBoZWxpY2FzZQ==[Qq]
[c]Kg==[Qq]
[f]Tm8uIEhlcmUmIzgyMTc7cyBhIGhpbnQuIEhlbGljYXNlIGlzIHRoZSBlbnp5bWUgdGhhdCBzcGxpdHMgb3BlbiB0aGUgcGFyZW50YWwgRE5BLCBjcmVhdGluZyB0aGUgcmVwbGljYXRpb24gZm9yay4=[Qq]

[q]In the diagram below, which number is DNA Polymerase III?

[textentry single_char=”true”]
[c]Mg ==[Qq]
[f]IFllcy4g4oCcMuKAnSBpcyBETkEgcG9seW1lcmFzZSBJSUksIHdoaWNoIHN5bnRoZXNpemVzIG5ldyBETkEgYnkgYXR0YWNoaW5nIG5ldyBudWNsZW90aWRlcyB0byB0aGUgMyYjODI0MjsgZW5kIG9mIGEgZ3Jvd2luZyBETkEgc3RyYW5kLg==[Qq]
[c]Kg==[Qq]
[f]Tm8uIEhlcmUmIzgyMTc7cyBhIGhpbnQuIEROQSBwb2x5bWVyYXNlIHN5bnRoZXNpemVzIG5ldyBETkEgYnkgYXR0YWNoaW5nIG5ldyBudWNsZW90aWRlcyB0byB0aGUgMyYjODI0MjsgZW5kIG9mIGEgRE5BIHN0cmFuZC4gVGhlIG5ldyBudWNsZW90aWRlcyBhcmUgc2hvd24gaW4gbGlnaHQgYmx1ZS4gV2hpY2ggZW56eW1lIHNob3duIGFib3ZlIHNlZW1zIHRvIGJlIGludm9sdmVkIHdpdGggdGhlc2UgbmV3IG51Y2xlb3RpZGVzPw==[Qq]

[q]In the diagram below, which number indicates the lagging strand?

[textentry single_char=”true”]
[c]Mw ==[Qq]
[f]IFllcy4g4oCcM+KAnSBpcyB0aGUgbGFnZ2luZyBzdHJhbmQu[Qq]
[c]Kg==[Qq]
[f]Tm8uIEhlcmUmIzgyMTc7cyBhIGhpbnQuIFRoZSBsYWdnaW5nIHN0cmFuZCBpcyB3aGVyZSBETkEgc3ludGhlc2lzIG9jY3VycyBpbiBhIGRpcmVjdGlvbiBvcHBvc2l0ZSB0byB0aGF0IG9mIHRoZSB0aGUgb3BlbmluZyByZXBsaWNhdGlvbiBmb3JrLCBhbmQsIGFzIGEgcmVzdWx0LCBoYXMgdG8gYmUgZnJhZ21lbnRhcnkuIFdoZXJlIGRvIHlvdSBzZWUgc3ludGhlc2lzIG1vdmluZyBhd2F5IGZyb20gdGhlIHJlcGxpY2F0aW9uIGZvcms/[Qq]

[q]In the diagram below, which number indicates an RNA primer?

[textentry single_char=”true”]
[c]NA ==[Qq]
[f]IFllcy4g4oCcNOKAnSBpcyBhbiBSTkEgcHJpbWVyLg==[Qq]
[c]Kg==[Qq]
[f]Tm8uIEhlcmUmIzgyMTc7cyBhIGhpbnQuIEROQSBwb2x5bWVyYXNlIElJSSBjYW4gb25seSBhdHRhY2ggbnVjbGVvdGlkZXMgdG8gYW4gZXhpc3Rpbmcgc3RyYW5kLiBJdCBjYW4mIzgyMTc7dCBpbml0aWF0ZSBhIG5ldyBzdHJhbmQgd2hlcmUgbm9uZSBleGlzdHMuIEluc3RlYWQsIGFuIGVuenltZSBjYWxsZWQgcHJpbWFzZSAoNSkgbGF5cyBkb3duIGEgc2hvcnQgc3RyYW5kIG9mIFJOQSAodGhlIHByaW1lciksIHdoaWNoIEROQSBwb2x5bWVyYXNlIElJSSB3aWxsIHVzZSBhcyBhIHN0YXJ0aW5nIHBvaW50IGZvciByZXBsaWNhdGlvbi4gRmluZCAjIDUgYW5kIHlvdSYjODIxNztsbCBoYXZlIHlvdXIgYW5zd2VyLg==[Qq]

[q]In the diagram below, which number indicates the leading strand?

[textentry single_char=”true”]
[c]Ng ==[Qq]
[f]IFllcy4g4oCcNuKAnSBpcyB0aGUgbGVhZGluZyBzdHJhbmQu[Qq]
[c]Kg==[Qq]
[f]Tm8uIFRoZSBsZWFkaW5nIHN0cmFuZCBpcyB0aGUgc3RyYW5kIHdoZXJlIEROQSBwb2x5bWVyYXNlIGlzIGZvbGxvd2luZyBoZWxpY2FzZSBhdCB0aGUgdGhlIG9wZW5pbmcgcmVwbGljYXRpb24gZm9yay4gRmluZCB0aGUgRE5BIHBvbHltZXJhc2UgdGhhdCYjODIxNztzIGZvbGxvd2luZyB0aGUgZm9yaywgYW5kIHlvdSYjODIxNztsbCBoYXZlIHlvdXIgYW5zd2VyLg==[Qq]

[q]In the diagram below, which number is pointing to the single-strand binding proteins?

[textentry single_char=”true”]
[c]OA ==[Qq]
[f]IFllcy4g4oCcOOKAnSBpcyBwb2ludGluZyB0byB0aGUgc2luZ2xlLXN0cmFuZCBiaW5kaW5nIHByb3RlaW5z[Qq]
[c]Kg==[Qq]
[f]Tm8uIFRoZSBzaW5nbGUtc3RyYW5kIGJpbmRpbmcgcHJvdGVpbnMgYmluZCB0byB0aGUgRE5BIGF0IHRoZSByZXBsaWNhdGlvbiBmb3JrLCBrZWVwaW5nIHRoZSBETkEgZnJvbSBjbG9zaW5nIHVwICh3aGljaCB3b3VsZCBlbmQgdGhlIHJlcGxpY2F0aW9uIHByb2Nlc3MuIExvb2sgZm9yIHRoZXNlIHByb3RlaW5zIGNsb3NlIHRvIHRoZSBvcGVuaW5nIG9mIHRoZSBmb3JrLg==

Cg==

[Qq]
[q]In the diagram of a replication bubble below, which letter is pointing to the leading strand?

[textentry single_char=”true”]
[c]Sg ==[Qq]
[f]IFllcy4g4oCcSuKAnSBpcyBwb2ludGluZyB0byB0aGUgbGVhZGluZyBzdHJhbmQuIFlvdSBjYW4gdGVsbCBiZWNhdXNlIHRoZSBzdHJhbmQgaXMgYmVpbmcgc3ludGhlc2l6ZWQgaW4gdGhlIHNhbWUgZGlyZWN0aW9uIGFzIHRoZSBvcGVuaW5nIHJlcGxpY2F0aW9uIGZvcmsu[Qq]
[c]Kg==[Qq]
[f]Tm8uIEZpbmQgdGhlIHN0YW5kIHdoZXJlIHN5bnRoZXNpcyBpcyBjb250aW51b3VzLCBhcyBETkEgcG9seW1lcmFzZSBmb2xsb3dzIGhlbGljYXNlLg==
Cg==[Qq]
[q]In the diagram of a replication bubble below, which letter is labeling an Okazaki fragment?

[textentry single_char=”true”]
[c]Sw ==[Qq]
[f]IFllcy4g4oCcS+KAnSBpcyBsYWJlbGluZyBhbiBPa2F6YWtpIGZyYWdtZW50LCBvbmUgb2YgdGhlIGZyYWdtZW50cyBvZiBETkEgc3ludGhlc2l6ZWQgYWxvbmcgdGhlIGxhZ2dpbmcgc3RyYW5kLg==[Qq]
[c]Kg==[Qq]
[f]Tm8uIEZpbmQgdGhlIHNob3J0IHN0cmV0Y2hlcyBvZiBmcmFnbWVudGFyeSBETkEgdGhhdCBhcmUgc3ludGhlc2l6ZWQgb24gdGhlIGxhZ2dpbmcgc3RyYW5kICh0aGUgc3RyYW5kIHdoZXJlIHN5bnRoZXNpcyBpcyBtb3ZpbmcgYXdheQ==IGZyb20gdGhlIHJlcGxpY2F0aW9uIGZvcmspLg==
Cg==[Qq]
[q]In the diagram of a replication bubble below, which letter is pointing to the lagging strand?

[textentry single_char=”true”]
[c]TA ==[Qq]
[f]IFllcy4g4oCcTOKAnSBpcyBwb2ludGluZyB0byB0aGUgbGFnZ2luZyBzdHJhbmQu[Qq]
[c]Kg==[Qq]
[f]Tm8uIEZpbmQgdGhlIHNob3J0IHN0cmV0Y2hlcyBvZiBmcmFnbWVudGFyeSBETkEuIFRoZXNlIGFyZSBPa2F6YWtpIGZyYWdtZW50cywgYW5kIHRoZXkmIzgyMTc7cmUgb25seSBzeW50aGVzaXplZCBvbiB0aGUgbGFnZ2luZyBzdHJhbmQu
Cg==

Cg==[Qq]

[q labels = “top”]

 

[l]DNA helicase

[fx] No. Please try again.

[f*] Good!

[l]parent strand

[fx] No, that’s not correct. Please try again.

[f*] Excellent!

[l]DNA polymerase III

[fx] No. Please try again.

[f*] Great!

[l]newly synthesized DNA

[fx] No. Please try again.

[f*] Excellent!

[q]Each of the following is a step in DNA replication. The correct order of these steps is
I. An enzyme connects the sugars and phosphates of adjacent nucleotides.
II. Following the base pairing rules, new nucleotides bond with the template strand
III. An enzyme separates the two strands

[c]SSwgSUksIElJSQ==[Qq]

[c]SUlJLCBJ SSwgSQ==[Qq]

[c]SUksIElJSSwgSQ==[Qq]

[f]Tm8uIFlvdSBoYXZlIHRoZSBvcmRlciByZXZlcnNlZC4=[Qq]

[f]WWVzLiBEdXJpbmcgcmVwbGljYXRpb24sIGZpcnN0IHRoZSBzdHJhbmRzIGFyZSBzZXBhcmF0ZWQuIFRoZW4gbmV3IG51Y2xlb3RpZGVzIGJvbmQuIFRoZW4gYW4gZW56eW1lIGNyZWF0ZXMgc3VnYXItcGhvc3BoYXRlIGJvbmRzIGJldHdlZW4gYWRqYWNlbnQgbnVjbGVvdGlkZXMu[Qq]

[f]Tm8uIEZvciBzdGVwIElJIHRvIG9jY3VyLCB0aGUgc3RyYW5kIG5lZWRzIHRvIGJlIG9wZW5lZCBzbyB0aGF0IG5ldyBudWNsZW90aWRlcyBjYW4gYm9uZC4=[Qq]

[q]The result of DNA replication is a new molecule composed of one new strand, and one old strand (from the parent molecule). A way to describe this is ______-______ replication.

[hangman]

[c]c2VtaS1jb25zZXJ2YXRpdmU=[Qq]

[f]R29vZCBKb2IhIFRoZSByZXN1bHQgb2YgRE5BIHJlcGxpY2F0aW9uIGlzIGEgbmV3IG1vbGVjdWxlIGNvbXBvc2VkIG9uIG9uZSBuZXcgc3RyYW5kLCBhbmQgb25lIG9sZCBzdHJhbmQgKGZyb20gdGhlIHBhcmVudCBtb2xlY3VsZSkuIEEgd2F5IHRvIGRlc2NyaWJlIHRoaXMgaXMgc2VtaS1jb25zZXJ2YXRpdmU=IHJlcGxpY2F0aW9u

Cg==

[Qq]

[q]The bonds that helicase breaks are [hangman] bonds.

[c]aHlkcm9nZW4=[Qq]

[f]UGVyZmVjdCEgVGhlIGJvbmRzIHRoYXQgaGVsaWNhc2UgYnJlYWtzIGFyZSA=aHlkcm9nZW4=IGJvbmRzLg==[Qq]

[q]During replication, each strand serves as a  [hangman] for the synthesis of a second strand.

[c]dGVtcGxhdGU=

Cg==

[Qq]

[q]During DNA replication, the key enzymes always move in a [hangman] prime to [hangman] prime direction (hint: write out the numbers).

[c]Zml2ZQ==[Qq]

[c]dGhyZWU=

Cg==

[Qq]

[q]When nucleotides are added to a growing DNA strand, they’re always added on the [hangman] prime side.(hint: write out the number).

[c]dGhyZWU=

Cg==

[Qq]

[q]The enzyme that opens up the double helix is [hangman].

[c]aGVsaWNhc2U=[Qq]

[q]Helicase first opens up the double helix at a sequence of bases called the origin of [hangman].

[c]cmVwbGljYXRpb24=

Cg==

Cg==

[Qq]

[q]The structure formed by two replication forks is called a replication [hangman].

[c]YnViYmxl

Cg==

[Qq]

[q]During replication, [hangman]-[hangman]-[hangman]-[hangman] prevent the double helix from rewinding.

[c]c2luZ2xl[Qq]

[c]c3RyYW5k[Qq]

[c]YmluZGluZw==[Qq]

[c]cHJvdGVpbnM=

Cg==

[Qq]

[q]After helicase opens up the double helix, [hangman] lays down a primer of RNA.

[c]cHJpbWFzZQ==[Qq]

[q]The job of DNA [hangman] 1 is to remove the RNA primer.

[c]cG9seW1lcmFzZQ==[Qq]

[q]The enzyme whose job it is to connect the fragments created during replication is [hangman].

[c]bGlnYXNl[Qq]

[x][restart]

[/qwiz]

What’s Next?

Please proceed to our next tutorial: Transcription