DNA Replication Exam 4

What are the roles of the following proteins in DNA: replication

Replication:

• _____ of replication: _____ _____ (sequences) where DNA replication _____

• _____ bubble: _____ area of _____ DNA

• _____ fork: site of active _____, two per _____ bubble

Replication:

• Origin of replication: specific sites (sequences) where DNA replication starts

• Replication bubble: expanding area of replicated DNA

• Replication fork: site of active replication, two per replication bubble

What are the roles of the following proteins in DNA: helicase

Helicase: _____ double-stranded DNA, but _____ the DNA in front of it, requiring action for _____ to reduce _____

Helicase: unwinds double-stranded DNA, but overwinds the DNA in front of it, requiring action for topoisomerase to reduce strain

What are the roles of the following proteins in DNA: topoisomerase

Topoisomerase: reduces _____ during _____ of DNA by making _____ _____ in DNA strands

Topoisomerase: reduces strain during unwinding of DNA by making temporary cuts in DNA strands

What are the roles of the following proteins in DNA: replication, helicase, primase

Primase: builds short _____ strands called _____ that DNA _____ can work from to _____ a _____ strand

Primase: builds short RNA strands called primers that DNA polymerase can work from to build a DND strand

What are the roles of the following proteins in DNA: DNA polymerase

DNA polymerase: add new _____ to the __’ end of a DNA strand

DNA polymerase: add new nucleotides to the 3’ end of a DNA strand

What are the roles of the following proteins in DNA: DNA ligase

DNA ligase: connects ______ strands of DNA together to combine ______ ______ to form one ______ new strand

DNA ligase: connects adjacent strands of DNA together to combine Alazaki fragments to form one continuous new strand

What are the differences between leading and lagging strand synthesis? What limitation of DNA polymerase creates this difference?

Leading:

• Continuous/Discontinuous?

•  synthesized _____ replication fork

Lagging:

• Continuous/Discontinuous?

• individual fragments synthesized _____ from fork

• A series of _____

• ___ polymerase _____ ___ primers with DNA

  limitation:

  • DNA _____ can only add nucleotides to the _' end of an existing strand (5' → 3' direction)

Leading:

• Continuous

•  synthesized toward replication fork

Lagging:

• Discontinuous

• individual fragments synthesized away from fork

• A series of fragments

• DNA polymerase replaces RNA primers with DNA

limitation:

• DNA polymerase can only add nucleotides to the 3' end of an existing strand (5' → 3' direction)

Which is the leading strand, and which is the lagging strand? How do you know? What are the 5’ and 3’ ends of each strand? How do you know? Where will new nucleotides be added?

• DNA strands are _____ (one runs 5’ → 3’, the other 3’ → 5’)

• New nucleotides added at the _’ end of DNA strand

• DNA strands are antiparallel (one runs 5’ → 3’, the other 3’ → 5’)

• New nucleotides added at the 3’ end of DNA strand

What is a telomere, and why are they necessary to protect our genes? What is the relationship between telomeres, telomerase, and cancer?

• Telomere: 

  • ______ repetitive sequence found at the end of ______

  • Act as a ______ to protect protein-coding genes

  • ______ with each replication

  • Limit ______ potential of cell → Prevents ______, but may contribute to short-term aging

  Telomerase: maintains telomere ______ in gamete-producing cells

  • Uses an ______ strand as a ______

  • Helps to ______ the ends of ______

  • It solves a problem with replicating linear chromosomes where they get ______

  • It helps to extend the number of times a cell can ______

• Telomere: 

  • Non-protein-coding repetitive sequence found at the end of chromosomes

  • Act as a buffer to protect protein-coding genes

  • Shorten with each replication

  • Limit replicative potential of cell → Prevents cancer, but may contribute to short-term aging

  Telomerase: maintains telomere length in gamete-producing cells

  • Uses an RNA strand as a template

  • Helps to lengthen the ends of chromosomes

  • It solves a problem with replicating linear chromosomes where they get shorter

  • It helps to extend the number of times a cell can divide