DNA replication

• What is the process of DNA replication?

  Making a complete copy of DNA
• Why is DNA replication important?

  It ensures continuity of hereditary information
• When does DNA replication occur?

  During the S-Phase of Interphase
• What are the three main steps of DNA replication?

  Initiation, elongation, and termination

  
• What are origins of replication?

  Starting points for DNA replication
• How many origins of replication do prokaryotic chromosomes have?

  One origin of replication
• How many origins of replication do eukaryotic chromosomes have?

  Multiple origins of replication
• What role does helicase play in DNA replication?

  It unwinds the two strands of DNA

  
• What are replication bubbles?

  Regions where DNA strands are unwound
• What is the function of single-stranded binding proteins?

  To keep DNA strands separated and stable
• What do topoisomerases do during DNA replication?

  They untangle supercoiling of DNA
• What is the role of primase in DNA replication?

  It synthesizes RNA primers for DNA synthesis

  
• Why are RNA primers necessary for DNA synthesis?

  DNA polymerases need a starting point

  
• What is the direction of DNA strand synthesis by DNA polymerase?

  5’ to 3’ direction

  
• How is the leading strand of DNA synthesized?

  Continuously in one piece
• How is the lagging strand of DNA synthesized?

  Discontinuously in Okazaki fragments

  
• What are Okazaki fragments?

  Short DNA segments on the lagging strand

  
• What enzyme joins Okazaki fragments together?

  Ligase
• What does it mean that DNA replication is semiconservative?

  Each new DNA has one original strand
• What is proofreading in DNA replication?

  Checking and correcting nucleotide errors
• What is mismatch repair?

  Correcting mis-paired bases after replication

  
• What is a telomere?

  A repetitive DNA region at chromosome ends
• What nucleotide sequence is typically found in telomeres?

  TTAGGG
• Why do telomeres shorten with each replication?

  DNA cannot be fully copied at the ends

  
• What happens when telomeres reach a critical length?

  Cells undergo apoptosis or stop dividing

  
• What is telomerase?

  An enzyme that lengthens telomeres
• When is telomerase active?

  During fetal development
• What happens to telomerase after fetal development?

  It shuts off and degrades over time
• How can telomerase lead to cancer?

  It can reactivate in mutated cells