The specificity of the PCR depends crucially upon the primers. The following factors are important in choosing effective primers

Primers should be 17 to 30 nucleotides in length

A GC content of about 50% is ideal. For primers with a low GC content, it is desirable to choose a long primer to avoid a low melting

 temperature.

Sequences with long runs (i.e., more than three or four) of a single nucleotide should be avoided.

TLS Online TPP Program

#Id: 2983

#Unit 3. Fundamental Processes

All prokaryotic and eukaryotic DNA polymerases share the same fundamental type of synthetic activity, antiparallel synthesis from 5' to 3' from a template that is 3' to 5'.

TLS Online TPP Program

#Id: 2985

#Unit 3. Fundamental Processes

A comprehensive series of such temperature-sensitive mutants in Escherichia coli identifies a set of loci called the dna genes. The dna mutants distinguish two stages of replication by their behavior when the temperature is raised

The members of the major class of quick-stop mutants cease replication immediately upon a temperature increase.

The members of the smaller class of slow-stop mutants complete the current round of replication, but cannot start another.

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. 

TLS Online TPP Program

#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.

TLS Online TPP Program

#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

TLS Online TPP Program

#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.