Phages have two important structural features that are common to all phages. The first structure, the _________, holds the genetic information or DNA. The second structure, the ___________, aids in attachment of the virus to the bacteria host species.

Capsid

Tail**** check this answer.

To find the answer to this question, we can start by understanding the basic characteristics of phages. Phages, also known as bacteriophages, are viruses that infect bacteria. They have two essential structural features that are common to all phages.

The first structure that holds the genetic information or DNA is known as the "head" or "capsid." The head is a protein shell that protects and encloses the phage's genetic material. It is typically icosahedral in shape, meaning it has a roughly spherical structure with 20 triangular faces.

The second structure that aids in attachment of the phage to the bacteria host species is called the "tail fibers" or "tail spikes." These are extensions protruding from the head of the phage. The tail fibers are responsible for recognizing and binding to specific receptor sites on the surface of the bacteria. This attachment mechanism allows the phage to inject its genetic material into the host bacterium and initiate the infection process.

Therefore, the first structure, which holds the genetic information or DNA, is the head or capsid, and the second structure, which aids in attachment to the bacteria host species, is the tail fibers or tail spikes.