Rudradeep Mukherjee’s Reviews > Molecular Genetics: An Introductory Narrative > Status Update

The RNA polymerase enzyme "plays" around with the DNA molecule to create the template for making proteins.

Discussion of "Genetic fine structure" was very obscure for me(another section which will require re-reading). That's the problem with an e-book(which has been loaned from Internet Archive). There are concepts I don't remember and referencing it from the previous pages is a mess. The overall view is clear as of now. At this point, the discussion moves to lysogenic bacteria(which carry phages instead of dying).

Mutants among T-phage viruses can be similarly used to make a genetic map of various properties. The process and crossovers are similar to that used in bacteria. [Skipped most of this section for re-reading]

Hershey-Chase experiment threw light on how T-even phages inject their DNA into the bacteria, leaving their protein bodies outside. Subsequent experiments showed that a tailless head and a headless tail can conjugate to make another virus. Smaller phages with singe-strand DNA utilise asymmetric replication to reproduce within cell.

Phages are smaller(around 1/1000th) than their bacterial prey. They have a tadpole like structure where the tail is used as a contact point with the bacterial surface. The structure is complex with core, sheath and tail like fibres. Under osmotic shock(from a highly saline solution to distilled water), the head ruptures to send out DNA. Shows a semipermeable membrane at head. T-even phage DNA differs in cytosine.

Apart from coding information for proteins, the structure of DNA paves the way for its replication as well. As DNA parts in the middle in sort of a zipping action, complementary strands pair up with the parting strands. Two new molecules of DNA are created.