AP Biology : Understanding Translation Processes

Study concepts, example questions & explanations for AP Biology

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Example Questions

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Example Question #153 : Dna, Rna, And Proteins

Which of the following processes converts mRNA codons into proteins?

Possible Answers:

Apoptosis

Glycolysis

Transcription

Replication

Translation

Correct answer:

Translation

Explanation:

Translation is the process of converting an mRNA codon sequence into protein via the ribosome, so that is the correct answer. Apoptosis is programmed cell death. Transcription is close, but it is the process of making RNA from DNA. Glycolysis is the process of creating two pyruvate molecules from glucose, and produces two ATP.

Example Question #1 : Understanding Translation Processes

Which of the following templates is used during translation?

Possible Answers:

microRNA

mRNA

tRNA

rRNA

DNA

Correct answer:

mRNA

Explanation:

mRNA is the template used during translation. The mRNA strand is read and "translated" into a polypeptide by tRNA.

DNA would be the template for transcription, not for translation.

Example Question #155 : Dna, Rna, And Proteins

Which of the following statements regarding codons is true?

Possible Answers:

The AUG codon begins the process of translation for every transcript of mRNA

The length of each codon is dependent on the amino acid it codes for

There is one codon for each amino acid

None of the other choices are correct

Correct answer:

The AUG codon begins the process of translation for every transcript of mRNA

Explanation:

Every codon is composed of three RNA nucleobases, and codes for a specific amino acid; however, there can be multiple codons that code for one amino acid. The start codon, AUG, signals the beginning of translation and codes for methionine.

Example Question #156 : Dna, Rna, And Proteins

Which of the following statements regarding translation is false?

Possible Answers:

There is only one stop codon (UAG) that signals the end of translation

There is only one start codon (AUG) that signals the beginning of translation

tRNA works to bring amino acids corresponding to the codons in the mRNA sequence to the ribosome

Adjacent amino acids in a sequence are joined via peptide bonds

Correct answer:

There is only one stop codon (UAG) that signals the end of translation

Explanation:

While there is only one start codon (AUG), but there are three different stop codons (UGA, UAG, and UAA) that can each signal for the end of translation, or termination. During the translation process, tRNA is used to bring amino acids (corresponding to the codons in the mRNA sequence) to the ribosome, which become attached via peptide bonds to form a polypeptide.

Example Question #2 : Understanding Translation Processes

Which of the following statements concerning the genetic code is false?

Possible Answers:

An amino acid can only be produced from one codon

tRNA will always carry one amino acid to the ribosome

More than one codon can code for the same amino acid

A codon will always code for the same amino acid

Correct answer:

An amino acid can only be produced from one codon

Explanation:

The genetic code is degenerative, meaning that multiple codons can code for the same amino acid. It is also unambiguous: a particular codon will always code for one amino acid. That being said, it would be wrong to assume that an amino acid will only have one codon, as an amino acid can have multiple different codons that code for it.

Example Question #3 : Understanding Translation Processes

Which of the following statements concerning translation is true?

Possible Answers:

The poly A tail serves as an attachment site for the ribosome

mRNA is read by the ribosome in 3'-to-5' direction

The first amino acid, methionine, is positioned in the A site of the ribosome

The growing amino acid chain is found in the P site of the ribosome

Correct answer:

The growing amino acid chain is found in the P site of the ribosome

Explanation:

In translation, the mRNA is positioned in the ribosome and read in the 5'-to-3' direction. Initiation of translation is triggered by a tRNA attached to a methionine entering the P site of the ribosome. The mRNA will then be read, and additional amino acids will be added to the chain, which grows in the P site. New tRNA enters the A site and old tRNA exits the E site, but the amino acid chain is always anchored to the tRNA in the P site.

Example Question #4 : Understanding Translation Processes

What happens when the ribosome encounters a stop codon?

Possible Answers:

A special terminal amino acid is placed on the polypeptide chain 

A chaperone is recruited to help fold the polypeptide chain

A release factor is recruited, which dissociates the translation complex and releases the completed polypeptide chain

An anticodon-codon pairing is made with a final tRNA that releases the completed polypeptide chain

Correct answer:

A release factor is recruited, which dissociates the translation complex and releases the completed polypeptide chain

Explanation:

Stop codons are a signal for the ribosome to recruit a release factor. Release factors are proteins that dissociate the translation complex and release the polypeptide chain.

There are no tRNAs that match stop codons and there is no "special" terminal amino acid. Chaperones are involved in folding proteins, but they are not involved in the termination of translation.

Example Question #1004 : Ap Biology

Where does translation occur?

Possible Answers:

The Golgi apparatus

The cytoplasm

The mitochondria

The nucleus

Correct answer:

The cytoplasm

Explanation:

Translation, the process of synthesizing a polypeptide from an mRNA template, primarily occurs in the cytoplasm. Another possible answer would be the rough endoplasmic reticulum. Both the rough endoplasmic reticulum and cytoplasm contain ribosomes, which are essential for translation.

The mitochondria are essential for cellular respiration, and are the site of the citric acid cycle and electron transport chain. The nucleus houses DNA and synthesizes ribosomes (in the nucleolus). The Golgi apparatus modifies and packages proteins in vesicles after translation is complete.

Example Question #5 : Understanding Translation Processes

Where could translation of RNA occur in the cell?

Possible Answers:

Nucleolus

Ribosomes on the rough endoplasmic reticulum

Mitochondria

Lysosome

Nucleus

Correct answer:

Ribosomes on the rough endoplasmic reticulum

Explanation:

After DNA is transcribed into RNA, the RNA goes through post-transcriptional modifications and is then sent out of the nucleus to the cytoplasm. From there, the mRNA is brought to the ribosomes, some located on the rough endoplasmic reticulum and some free-floating, in order to be translated into proteins. Proteins are then packaged and transported to their respective locations for usage.

The nucleolus is responsible for synthesizing and assembling ribosomal subunits. The nucleus houses DNA and is the site of transcription, but not translation. Mitochondria are essential for cellular respiration and ATP synthesis. Lysosomes digest cellular wastes and defective proteins.

Example Question #6 : Understanding Translation Processes

During translation, amino acid elongation continues until __________.

Possible Answers:

all tRNA molecules are empty

no further amino acids are needed

the ribosome reads a stop codon

the polypeptide is long enough for folding to begin

the ribosome reaches the end of the mRNA strand

Correct answer:

the ribosome reads a stop codon

Explanation:

Elongation continues until a stop codon occupies the A-site of the ribosome. The stop codon is a three-base signal present within the mRNA. There are three stop codons: UAG, UAA, and UGA.

There are three principle steps to translation. Initiation occurs when the ribosomes encounters the start codon, AUG, and recruits a methionine tRNA. Elongation of the polypeptide occurs as the ribosomes continues to recruit tRNA molecules and build the peptide chain. Termination occurs when the ribosome encounters a stop codon and releases the completed polypeptide.

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