O

Ochre Codon:

It is the triplet UAA, one of the three codons that cause the termination of protein synthesis.

Okazaki Fragments:

These are short stretches of 1000-2000 bases produced during discontinous replication; they are later joined into a covalently intact strand.

Oncogenes:

These are the genes whose products have the ability to transform the eukaryotic cells so that they grow in a manner analogous to tumor cells.

Open Reading Frame:

It contains a series of triplets coding for amino acids without any termination codons.

Operon:

It is a unit of bacterial gene expression and regulation, including structural genes and control elements in DNA recognised by regulator gene products.

Origin of Replication:

A site at which DNA replication is initiated. There is only one in bacterial chromosomes, but numerous origins in eukaryotic chromosomal DNA.

Overlapping Clones:

Collection of cloned sequences made by generating randomly overlapping DNA fragments with infrequently cutting restriction enzymes.