Q.Explain the structure of T-even bacteriophages.

T-even bacteriophages (e.g., T2, T4, T6) have a distinctive two-part structure — a DNA-containing polyhedral head and a specialised, contractile tail used for infecting bacteria.

T-even bacteriophages are viruses that infect bacteria (e.g., E. coli), and are structurally among the most complex viruses known. Their structure has two main parts:

1. Head:

• The head is polyhedral (icosahedral) in shape.
• It encloses the phage's genetic material — double-stranded DNA, tightly packed within.
• The head is covered by a protein coat (capsid) made of capsomeres.

2. Tail:

The tail is a complex structure attached to the head, consisting of:

• A hollow core (central tube), through which the DNA is injected into the host cell during infection.
• A contractile sheath surrounding the hollow core — this sheath contracts during infection, driving the core through the bacterial cell wall.
• A collar, connecting the head to the tail.
• A hexagonal base plate at the very end of the tail, from which project several tail pins (spikes) and tail fibers. …