Homoplasy is similarity arrived at via independent evolution.

TLS Online TPP Program

#Id: 2986

#Unit 3. Fundamental Processes

In E. coli., DNA polymerase III, a multisubunit protein, is the replication polymerase responsible for de novo synthesis of new strands of DNA. 

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#Id: 2988

#Unit 3. Fundamental Processes

In E. coli DNA polymerase II is required to restart a replication fork when its progress is blocked by damage in DNA.

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#Id: 2989

#Unit 3. Fundamental Processes

In E. coli., DNA polymerases IV and V are involved in allowing replication to bypass certain types of damage and are called error-prone polymerases

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#Id: 2990

#Unit 3. Fundamental Processes

In E. coli., DNA polymerase I (coded by polA) is involved in the repair of damaged DNA and, in a subsidiary role, in semiconservative replication.

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#Id: 2992

#Unit 3. Fundamental Processes

DNA polymerase I has a unique 5 '-3' exonuclease activity that can be combined with DNA synthesis to perform nick translation.

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#Id: 2993

#Unit 3. Fundamental Processes

The first DNA-synthesizing enzyme to be characterized was DNA polymerase I, which is a single polypeptide of 103 kD, The chain can be cleaved into two parts by proteolytic treatment.

The larger cleavage product (68 kD) is called the Klenow fragment. It is used in synthetic reactions in vitro, It contains the polymerase and the proofreading 3'-5'  exonuclease activities.

The small fragment (35 kD) possesses a 5 '-3' exonucleolytic activity, which excises small groups of nucleotides, up to - 10 bases at a time. This activity is coordinated with the synthetic/ proofreading activity. It provides DNA polymerase I with a unique ability to start replication in vitro at a nick in DNA.