D1.1  DNA Replication

Guiding Questions:  
Guiding questions help students view the content of the syllabus through the conceptual lenses of both the themes and the levels of biological organization.

• How is new DNA produced? 
• How has knowledge of DNA replication enabled applications in biotechnology?

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​Linking Questions:  
Linking questions strengthen students’ understanding by making connections between topics.  The ideal outcome of the linking questions is networked knowledge.

• How is genetic continuity ensured between generations? 
• What biological mechanisms rely on directionality?

Resources:

• At SHS, Topic D1.1 is taught in the Nucleic Acids and DNA Replication units. 
• Quizlet study set for this topic.  Coming soon!
• View the general sequence of the SHS course
• View the SHS units mapped to the IB Biology curriculum roadmap

D1.1.1— DNA replication as production of exact copies of DNA with identical base sequences.

• State that DNA replication is the production of exact copies of DNA with identical base sequences. 
• Outline the purposes of DNA replication.​

D1.1.2— Semi-conservative nature of DNA replication and role of complementary base pairing.

• Describe the meaning of “semi conservative” in relation to DNA replication.
• Explain the role of complementary base pairing in DNA replication.

D1.1.3— Role of helicase and DNA polymerase in DNA replication.

• State why DNA strands must be separated prior to replication.
• Outline the role of helicase in DNA replication. 
• Outline the role of DNA polymerases in DNA replication.
• State that there are separate DNA polymerases for each stand of template DNA.

D1.1.4-- Polymerase chain reaction and gel electrophoresis as tools for amplifying and separating DNA.

• State the function of the PCR.
• Outline the process of the PCR, including the use of primers, temperature changes and Taq polymerase.
• Deduce the number and relative size of DNA fragments from the number of bands in an electrophoresis gel. 
• Outline the procedure for DNA electrophoresis.
• Describe how and why DNA fragments separate during electrophoresis.​ ​

D1.1.5— Applications of polymerase chain reaction and gel electrophoresis.  

• List applications of the PCR.
• Outline the use of the PCR in testing for viral infection.
• Discuss advantages and disadvantages of using the PCR test for viral infections.
• Outline the process of DNA profiling.
• List applications of DNA profiling.
• Analyze a DNA profile to determine relatedness or forensic guilt. 
• List example sources of DNA that can be used in DNA profiling.​

AHL ​​​​D1.1.6- Directionality of DNA polymerases.

• Identify the 5’ ends and 3’ ends of a strand of DNA.
• Describe the formation of the covalent bond between adjacent nucleotides during DNA replication. 
• State that DNA polymerases can only add free nucleotides to an existing DNA strand. 
• State that DNA polymerases can only add the 5’ phosphate of a free nucleotide to the 3’ deoxyribose of the elongating strand.

AHL ​​​​D1.1.7- Differences between replication on the leading strand and the lagging strand.

• Explain why replication is different on the leading and lagging strands of DNA.
• Compare the pace and direction of replication on the leading and lagging strands of DNA.
• Outline the formation of Okazaki fragments on the lagging strand.

AHL ​​​​D1.1.8- Functions of DNA primase, DNA polymerase I, DNA polymerase III and DNA ligase in replication.

• Explain the need for RNA primers in DNA replication.
• Compare the number of RNA primers on the leading and lagging strands.
• Outline the function of the enzyme DNA primase.
• Outline the function of the enzyme DNA polymerase III. 
• Outline the function of the enzyme DNA polymerase I. 
• Explain why there are gaps between adjacent Okazaki fragments on the lagging strand. 
• Outline the function of the enzyme DNA ligase.

AHL ​​​​D1.1.9- DNA proofreading.

• State the function of DNA proofreading. 
• Outline the process of DNA proofreading by DNA polymerase III.