(Unit 1.2) DNA Replication

• What is the significance of the three prime and five prime ends of DNA in replication?

  They determine the direction in which DNA can be added during replication
• What happens to DNA during mitosis?

  DNA is duplicated or replicated
• What is the process called where the DNA double helix makes an exact copy of itself?

  DNA replication
• What breaks the weak hydrogen bonds during DNA replication?

  The unwinding of the DNA double helix
• What is the leading strand in DNA replication?

  The strand that is synthesized continuously in the 5' to 3' direction
• How does the lagging strand differ from the leading strand during DNA replication?

  The lagging strand is replicated in fragments, while the leading strand is continuous
• What are primers in the context of DNA replication?

  Short complementary sequences of nucleotides required to start a new DNA strand
• What role does DNA polymerase play in DNA replication?

  It adds complementary nucleotides to the growing DNA strand
• What is the function of ligase in DNA replication?

  It joins together the fragments of the lagging strand
• Why is ATP required during DNA replication?

  It provides the energy necessary for the replication process
• What is the purpose of a thermal cycler in PCR?

  It cycles through different temperatures to facilitate DNA replication
• What happens during the first step of PCR when the temperature is raised to 92-90 degrees Celsius?

  It breaks the weak hydrogen bonds between the DNA strands
• What occurs during the second step of PCR when the temperature is lowered to 50-65 degrees Celsius?

  Primers bond to the separated DNA strands
• What is the significance of using heat-tolerant DNA polymerase in PCR?

  It can withstand the high temperatures used during the PCR process
• What are the requirements for PCR to take place?

  • Original DNA template strand
  • Primers
  • Supply of nucleotides
  • pH buffer for optimum conditions
  • Heat-tolerant DNA polymerase
• How does PCR amplify DNA?

  By repeating cycles of heating and cooling to create multiple copies of DNA
• What is the role of a pH buffer in PCR?

  To maintain optimum pH conditions during the reaction
• What is the outcome of one cycle of PCR?

  Two identical strands of DNA are produced from one original strand
• What are the uses of PCR?

  • Forensics: amplifying DNA from crime scenes
  • Paternity testing: determining biological relationships
  • Medical testing: checking for genetic disorders
• what are the stages of the leading strand?

  1. hydrogen bonds break and DNA unzips
  2. DNA primers attach to the start of the piece of DNA that is being copied
  3. DNA polymerase attaches free nucleotides to the 3' end of the primer
  4. This is a continuous process until leading strand has been copied.
• what are the stages for the lagging strand?

  1. many primers attach along the lagging strand
  2. these are extended by DNA Polymerase
  3. these fragments then join together by the enzyme ligase
  4. this is a discontinuous process, creating the lagging strand.
• what is PCR?


  PCR allows specific sections of DNA to be amplified in Vitro
• what happens during the 1st cycle of PCR

  1. DNA is heated to 95 degrees, causes DNA to denature and strands to separate
  2. DNA cooled to 50-65 degree, allows short primers bond to separated DNA strands
  3. DNA heated again to 72 degree, allows heat-tolerant DNA polymerase to replicate DNA