Gene Expression And Regulation Questions! Trivia Quiz

1.

Translation occurs in the:

A.

Nucleolus.
B.

Golgi apparatus.
C.

Cytoplasm.
D.

Intercellular space.
E.

Center of a black hole.

Correct Answer
C. Cytoplasm.

Explanation
Translation is the process by which the genetic information stored in mRNA molecules is used to synthesize proteins. This process takes place in the cytoplasm of the cell, specifically on the ribosomes. The cytoplasm is the fluid-filled region between the cell membrane and the nucleus, where many cellular processes occur. The nucleolus is responsible for the production of ribosomes, not translation. The Golgi apparatus is involved in the modification and packaging of proteins, but not in translation. The intercellular space refers to the region between cells, which is not involved in translation. The center of a black hole is not relevant to cellular processes.

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2.

Alanyl-tRNA synthetase joins the amino acid alanine to its specific tRNA. It is an example of the class of enzymes called ________.

Correct Answer
aminoacyl-tRNA synthetases
aminoacyl-tRNA synthetase
aminoacyl tRNA synthetases
aminoacyl tRNA synthetase

Explanation
The correct answer is aminoacyl-tRNA synthetases. Aminoacyl-tRNA synthetases are a class of enzymes that catalyze the attachment of specific amino acids to their corresponding tRNA molecules. Alanyl-tRNA synthetase is an example of this class of enzymes, as it specifically joins the amino acid alanine to its specific tRNA molecule. Therefore, the correct answer options all refer to this class of enzymes.

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3.

A base at the 5' end of the codon hydrogen bonds with a base at the ___' end of the anticodon.

Correct Answer
3
3'

Explanation
The base at the 5' end of the codon hydrogen bonds with a base at the 3' end of the anticodon. This is because in DNA and RNA, the two strands are antiparallel, meaning they run in opposite directions. The 5' end of one strand is paired with the 3' end of the other strand. In the context of codons and anticodons, the codon is found on the mRNA molecule and the anticodon is found on the tRNA molecule. The pairing of the bases through hydrogen bonds ensures the correct amino acid is added to the growing protein chain during translation.

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4.

There is more than one codon for most amino acids. That is, the genetic code is _______.

Correct Answer
degenerate

Explanation
The term "degenerate" refers to the fact that there is more than one codon for most amino acids in the genetic code. This means that multiple codons can code for the same amino acid. This redundancy in the genetic code allows for some flexibility and robustness in protein synthesis. It also helps to protect against errors during DNA replication or transcription, as a mutation in the DNA sequence may still result in the same amino acid being incorporated into the protein due to the degeneracy of the genetic code.

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5.

When a new charged tRNA arrives at the ribosome to participate in translation, it binds to the _______ site of the ribosome.

Correct Answer
A
A site
aminoacyl
aminoacyl site

Explanation
When a new charged tRNA arrives at the ribosome to participate in translation, it binds to the A site of the ribosome. The A site, also known as the aminoacyl site, is where the incoming tRNA carrying the next amino acid in the growing polypeptide chain binds to the ribosome. This binding allows the ribosome to add the amino acid to the growing chain during the process of translation.

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6.

In eukaryotes, translation (almost) always begins with the codon AUG and the first amino acid added to the polypeptide is _______, which is coded by this codon. (We didn't cover this one this year, 2010).

Correct Answer
methionine

Explanation
In eukaryotes, translation typically starts with the codon AUG, which codes for the amino acid methionine. Methionine is often referred to as the "start" codon because it initiates the process of translation by being the first amino acid added to the growing polypeptide chain.

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7.

N-formyl methionine is the first amino acid added to a new polypeptide in _______. (We didn't cover this one this year, 2010).

Correct Answer
E. coli
bacteria
prokaryotes

Explanation
N-formyl methionine is the first amino acid added to a new polypeptide in E. coli, bacteria, and prokaryotes. This implies that these organisms use N-formyl methionine as the initiator amino acid during protein synthesis.

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8.

Prokaryotes mRNAs code for more than one polypeptide, that is, they are _________ mRNAs.

Correct Answer
polycistronic

Explanation
Prokaryotes have a unique characteristic where their mRNAs can code for multiple polypeptides. This means that a single mRNA molecule can carry the instructions for the synthesis of multiple proteins. This type of mRNA is referred to as polycistronic mRNA. It allows prokaryotes to efficiently coordinate the expression of multiple genes and produce multiple proteins simultaneously from a single mRNA transcript.

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9.

Several ribosomes can be translating a mRNA at the same time. When seen under the electron microscope, this cluster of ribosomes is called a _______. (We didn't cover this one this year, 2010).

Correct Answer
polyribosome
polysome

Explanation
A polyribosome, also known as a polysome, is a cluster of ribosomes that are simultaneously translating a single mRNA molecule. This allows for the production of multiple copies of the same protein at the same time.

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10.

When the codon _______, which is one of the three possible terminator (nonsense, stop) codons, is in the aminoacyl position of the ribosome, translation termination occurs.

Correct Answer
UAA
UGA
UAG

Explanation
When the codon UAA, UGA, or UAG is in the aminoacyl position of the ribosome, translation termination occurs. These three codons are known as terminator or stop codons because they signal the end of protein synthesis. When a ribosome encounters one of these codons, it releases the newly synthesized protein and disassembles, completing the process of translation.

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11.

If a tRNA had the anticodon: 5' CUU 3', then the amino acid it is attached to is _______. (Careful! Remember codon-anticodon pairing is antiparallel.)

Correct Answer
lys
lysine

Explanation
The anticodon of the tRNA is CUU. In the genetic code, CUU codes for the amino acid lysine. Therefore, the tRNA is attached to the amino acid lysine.

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12.

During tRNA charging, an amino acid always attaches to a nucleotide that has the nitrogen base _______.

Correct Answer
adenine

Explanation
During tRNA charging, an amino acid always attaches to a nucleotide that has the nitrogen base adenine. This is because adenine forms a specific base pair with uracil, which is present in the anticodon region of tRNA molecules. The attachment of the amino acid to adenine ensures that the correct amino acid is added to the tRNA molecule, allowing it to properly match with the corresponding codon on the mRNA during protein synthesis.

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13.

The CCA nucleotide triplet is added to the ___' end of the tRNA.

Correct Answer
3
3'

Explanation
The CCA nucleotide triplet is added to the 3' end of the tRNA. The 3' end refers to the end of the tRNA molecule that has a free hydroxyl group (-OH) attached to the 3rd carbon of the last nucleotide. This CCA sequence is important because it serves as the attachment site for the amino acid during the process of protein synthesis. The amino acid is covalently bonded to the tRNA molecule at the 3' end through an ester bond, forming an aminoacyl-tRNA molecule.

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14.

During translation, the codon CUU always codes for leucine. That is, the genetic code is _______.

Correct Answer
non-ambiguous
nonambiguous
non ambiguous
not ambiguous

Explanation
The given correct answer is "non-ambiguous" or "not ambiguous". This means that when the codon CUU is encountered during translation, it always codes for the amino acid leucine. The genetic code is clear and specific in this case, leaving no room for multiple interpretations or ambiguity.

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15.

MRNAs have a segment at the 5' end and at the 3' end that is not translated into polypeptide (the part before the initiator codon and after the terminator codon). This region is called the ______.

Correct Answer
UTR
untranslated region

Explanation
mRNAs have specific regions at the 5' and 3' ends that are not translated into polypeptide chains. These regions are known as UTRs or untranslated regions. The UTRs include the part before the initiator codon (start codon) and after the terminator codon (stop codon). These regions play important roles in regulating gene expression, mRNA stability, and translation efficiency. The UTRs contain binding sites for regulatory proteins and microRNAs, which can influence the translation and stability of the mRNA molecule.

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16.

The process of adding an amino acid to the 3' end of a tRNA is called _______.

Correct Answer
charging
tRNA charging
aminoacylation
amino acylation

Explanation
The process of adding an amino acid to the 3' end of a tRNA is called charging. It is also known as tRNA charging, aminoacylation, or amino acylation.

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