When the ribosome reaches a stop codon on the mrna, no corresponding trna enters the a site. if the translation reaction were to be experimentally stopped at this point, which of the following would you be able to isolate. (a) an assembled ribosome with a polypeptide attached to the trna in the p site (b) separated ribosomal subunits, a polypeptide, and free trna (c) an assembled ribosome with a separated polypeptide (d) separated ribosomal subunits with a polypeptide attached to the trna (e) a cell with fewer ribosomes

The best answer to the question: When the ribosome reaches a stop codon on the mRNA, no corresponding tRNA enters the A site. If the translaton reaction were to be experimentally stopped at this point, which of the following would you be able to isolate, would be, A: An assembled ribosome with a polypeptide attached to the tRNA in the P site.

Explanation:

When mRNA is ready to be translated, ribosomal units assemble around the chain to begin the translation. In order for this translation to be correct, and follow a specific, and desired, pattern, the ribosome counts with a series of sites that, when they meet the appropriate signals in the mRNA sequences, it will know when to stop assembling tRNA and with it polypeptides. As such, once a ribosome meets what is known as a stop codon, tRNA and its consequently binding parts of a protein will also stop.

The P site is the second binding site for tRNA in a ribosome. During translation the P site is the one responsible for holding together tRNA and its attaching and growing polypeptide chain. When the process is ended by reaching a stop codon, the bond between the peptydil at the P site and tRNA is broken and the new protein is thus released. Therefore, if in a hypothetical situation, you were to stop the translation process precisely at the point where tRNA has entered the A site, which is the beginning of the translation sequence, you would be able to find the assembled ribosome, and the growing polypeptide chain attached to the already started tRNA on the P site.

(A)an assembled ribosome with a polypeptide attached to the tRNA in the P site.

Explanation:

When the ribosome reaches a stop codon (UAG, UGA or UAA) on the mRNA no tRNA enters the A site resulting in the ending of  the elongation process and the  beginning of the termination process. In the termination process a release factor joins the stop codon separating the ribosomal subunits, cutting the tRNA from the amino acids chain and the tRNA  separates from the P site.

If we stop the process in the elongation process we would be able to isolate an assemble ribosome with a polypeptide attached to the tRNA in the P site  due to the fact that the termination process did not start and what occurs in the last process in order to have a protein as described above has not been done.