The chemical knives of $DNA$ are
Ligases
Polymerases
Endonucleases
Transcriptases
The structure present over chromosome is
Substances known as 'heredity carriers' are
Which of the following inhibits protein synthesis by binding to $50 S$ ribosome
An unfertilized human egg contains
An inactive repressor produced by regulator gene that does not block the operator site in the tryptophan Operon is called