Biochem Exam 2 DNA Replication ppt

The _____________ model of DNA replication is the parental and daughter DNA are interspersed in both strands following replication.

The ______________ model of DNA replication says both parental strands stay together after DNA replication.

The ________________ model of DNA replication says the double-stranded DNA contains one parental and one daughter-in-law strand following replication.

Which model is correct for DNA replication?

• Conservative

• Semiconservative

• Dispersive

What are the features of DNA synthesis?

• DNA polymerase I forms phosphodiester bond

• DNA polymerase "finds" the correct complementary dNTP at each step in the lengthening process

• Direction of synthesis is 5' to 3'

• Direction of synthesis is 3' to 5'

3' to 5' exonuclease activity:

• functions in DNA replication and repair

• ability to remove nucleotides from the 3' end of the chain

• important for proofreading

5' to 3' exonuclease activity:

• ability to remove nucleotides from the 3' end of the chain

• functions in DNA replication and repair

Special conditions for eukaryotic DNA replication:

• copying of chromosomes only occurs during the S phase of the cell cycle

• Cell will not enter the mitotic phase unless all the DNA has replicated

• chromosomes must be attached to the mitotic spindle for mitosis to complete

• checkpoints in the system include proteins called cyclins and enzymes called cyclin-dependent kinases (Cdks)

• cells must be large enough, and enough proteins and nucleotides must be present

Polymerase alpha

• repair DNA

• replicate mitochondrial DNA

• synthesizes the RNA primer, initiates DNA synthesis and the lagging strand

• Synthesizes the leading strand, filling DNA gaps after removal of primer

Polymerase beta:

• synthesizes the RNA primer, initiates DNA synthesis and the lagging strand

• synthesizes the leading strand, filling DNA gaps after removal of primer

• Repair DNA

• replicate mitochondrial DNA