GRE Subject Test: Biology : Understanding Translation

Study concepts, example questions & explanations for GRE Subject Test: Biology

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Example Questions

Example Question #1 : Understanding Translation

A protein that will be embedded in the plasma membrane is likely to be translated by __________

Possible Answers:

ribosomes bound to the endoplasmic reticulum

ribosomes bound to the Golgi apparatus

cytosolic ribosomes

nuclear ribosomes

Correct answer:

ribosomes bound to the endoplasmic reticulum

Explanation:

Most proteins that will be embedded in the plasma membrane are translated on ribosomes located in the rough endoplasmic reticulum. There are specific mechanisms and proteins that help insert the proteins into the membrane while they are being translated. Free-floating proteins are more likely to be translated in the cytosol. The nucleus and the Golgi do not have ribosomes used for translation, though the Golgi can play an important role in transporting proteins from the rough endoplasmic reticulum to the membrane.

Example Question #2 : Understanding Translation

What site in the ribosome contains the elongating polypeptide?

Possible Answers:

R site

E site

A site

P site

Correct answer:

P site

Explanation:

A tRNA that is attached to one amino acid will enter the ribosomal complex at the A site. It will then receive the growing polypeptide chain from the previous tRNA and move into the P site. Once handing off the chain, the tRNA that no longer has an amino acid will exit the ribosome at the E site.

The peptide chain is always anchored in the P site, where peptide bond synthesis occurs.

Example Question #3 : Understanding Translation

Which of the following is true concerning the genetic code?

Possible Answers:

An amino acid has only one codon

A codon codes for one amino acid

One codon can code for multiple amino acids

Translation typically ends once the whole mRNA is read by the ribosome

Correct answer:

A codon codes for one amino acid

Explanation:

The genetic code is unambiguous, meaning that each given codon will always code for the same amino acid. An amino acid, however, can be coded for by multiple codons, making the genetic code degenerative in nature. Once a stop codon is reached during translation, the ribosome stops making the protein.

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