Several ribosomes attached to a single mRNA

Explanation

### Step-by-Step Solution:

1. **Understanding mRNA**: Messenger RNA (mRNA) is a type of RNA that carries genetic information from DNA to the ribosome, where proteins are synthesized.

2. **Role of Ribosomes**: Ribosomes are the cellular machinery responsible for translating the mRNA sequence into a polypeptide chain (protein). They read the mRNA in sets of three nucleotides (codons) and assemble amino acids in the correct order.

3. **Polysome Formation**: When multiple ribosomes attach to a single mRNA strand, they can simultaneously translate it. This structure is known as a polysome (or polyribosome).

...