replication

• What are the general characteristics of DNA replication?

  It is semiconservative, bidirectional, and semidiscontinuous.

  
• In which direction does DNA replication proceed?

  DNA replication proceeds in the 5’-3’ direction.

  
• What does semiconservative replication mean?

  • One strand is from the original template molecule.
  • One strand is newly synthesized.
  • Each DNA strand serves as a template for a new strand.
  • Produces 2 new DNA molecules, each with one new and one old strand.

  
• What is bidirectional replication?

  • Parent strands are unwound and replicated simultaneously.
  • Two replication forks are formed.
  • Initiates at a unique point called the origin (OriC).

  
• What does semi-discontinuous replication refer to?

  • Continuous for the leading strand.
  • Discontinuous for the lagging strand.
  • Overall process is described as semi-continuous.
• What is the direction of DNA synthesis?

  DNA synthesis always proceeds in a 5’ -> 3’ direction.
• How does the synthesis of the leading strand occur?

  It occurs in the 5’ -> 3’ direction, same as the replication forks.

  
• What are Okazaki fragments?

  They are short pieces synthesized discontinuously on the lagging strand.
• What is required for DNA synthesis?

  A template DNA strand and a primer are required.
• What is the role of the primer in DNA synthesis?

  The primer is a segment of RNA with a free 3’ hydroxyl group for nucleotide addition.
• What is the processivity of DNA polymerase?

  It is the average number of nucleotides added before a polymerase dissociates.
• What degrades DNA?

  DNA is degraded by nucleases.
• What are the types of nucleases?

  • DNases: degrade DNA.
  • Endonucleases: degrade nucleic acids at specific internal sites.
  • Exonucleases: degrade nucleic acids from one end.
• What is the function of DNA polymerase I?

  It is involved in recombination and repair, with both polymerase and exonuclease activity.

  
• What is the role of DNA polymerase III?

  It is the main enzyme for replication in E. coli with maximum polymerization and processivity rates.

  
• What is a replisome?

  • A group of proteins involved in replication.
  • Includes DNA polymerase I and III.
  • Contains helicase, topoisomerase, SBB proteins, primase, and DNA ligase.

  
• How accurate is DNA replication?

  DNA replication occurs with an extraordinary level of fidelity.
• What is proofreading in DNA replication?

  It allows the enzyme to remove newly made nucleotide incorporation errors.
• What are the stages of DNA replication?

  1. Initiation: regulated phase, occurs once per cell cycle.
  2. Elongation: DNA polymerase synthesizes new strands.
  3. Termination: occurs when no template remains or replication forks meet.
• What happens during the termination stage of DNA replication?

  Replication continues until no template remains or two replication forks meet.

  
• What is the role of RNAase H in DNA replication?

  RNAase H removes the RNA primer at the beginning of each Okazaki fragment.

  
• What is the function of DNA ligase?

  DNA ligase seals the nicks between Okazaki fragments to create a complete strand.

  
• How does eukaryotic DNA replication differ from prokaryotic replication?

  • Slower replication rate.
  • Many origins of replication.
  • Shorter Okazaki fragments.
  • Complex process finishing with telomere replication.
• What are telomeres?

  Structures at the end of eukaryotic chromosomes consisting of oligonucleotide repeats.
• What is the function of telomerase?

  Telomerase allows replication of the ends to prevent telomere shortening.
• What type of enzyme is telomerase?

  It is a reverse transcriptase.
• In which cells is telomerase active?

  It is active in germ cells and totipotent cells.