Question 1

A direct correlation exists between the level of translation and the length of a poly(A) tail.

Accepted Answer

The length of a poly(A) tail in mRNA molecules directly influences their translation efficiency; longer poly(A) tails generally enhance the stability and translation of the mRNA.

Question 2

Which of the following is part of posttranslational modification?

Accepted Answer

Posttranslational modification refers to the chemical modification of proteins after they have been synthesized, which can affect their function, localization, or stability.

Question 3

Eukaryotic genes are organized into operons.

Accepted Answer

Eukaryotic genes are typically not organized into operons; this form of gene organization is more common in prokaryotes. In eukaryotes, genes are usually regulated individually.

Question 4

Eukaryotic genes consist of protein-coding sequences and adjacent regulatory sequences.

Accepted Answer

Eukaryotic genes indeed consist of protein-coding sequences, known as exons, and adjacent regulatory sequences, which include promoters, enhancers, and other elements that control the expression of the gene.

Question 5

Which statement refers to genomic imprinting?

Accepted Answer

Genomic imprinting involves the silencing of an allele of a gene during gametogenesis, leading to the expression of only the maternal or paternal allele in the offspring.

Question 6

Pepsin, a digestive enzyme that degrades proteins in the stomach, is synthesized as pepsinogen and converted to active pepsin in the stomach by the removal of several amino acids. What is the activation of pepsin an example of?

Accepted Answer

The activation of pepsin from pepsinogen involves the modification of the enzyme after it has been translated, which is a form of posttranslational regulation. This process does not involve changes at the transcriptional, translational, or posttranscriptional levels.

Question 7

What is the role of a tumour suppressor protein in a cell?

Accepted Answer

Tumor suppressor proteins help prevent uncontrolled cell growth by slowing or halting cell division in abnormal cells, thereby acting as a safeguard against cancer development.

Question 8

Each steroid hormone can bind to its own steroid hormone response unit (SHRU) but NOT to the SHRU associated with other steroid hormones.

Accepted Answer

Each steroid hormone has its own specific SHRU, and it cannot bind to the SHRU of other steroid hormones.

Question 9

The DNA that encodes siRNA is NOT normally found in the nucleus.

Accepted Answer

siRNA is generated from double-stranded RNA in the cytoplasm, not from DNA in the nucleus.

Question 10

RNAi is a key regulator of transcription.

Accepted Answer

RNAi (RNA interference) primarily regulates gene expression at the post-transcriptional level by targeting mRNA for degradation or inhibiting its translation into protein.

Question 11

When DNA is imprinted, the methylation pattern is preserved.

Accepted Answer

During DNA imprinting, methylation patterns are established that mark the DNA, preserving these patterns through cell division and contributing to the regulation of gene expression based on the parent of origin.

Question 12

Which of the following genes encode proteins that generally stimulate cell division in normal cells?

Accepted Answer

Proto-oncogenes encode for proteins that help to regulate cell growth and differentiation. When these genes are mutated, they can become oncogenes, leading to uncontrolled cell division.

Question 13

Any gene could, theoretically, be specifically silenced by RNAi.

Accepted Answer

RNA interference (RNAi) is a biological process in which RNA molecules inhibit gene expression or translation, by neutralizing targeted mRNA molecules. Theoretically, any gene can be silenced by designing small interfering RNAs (siRNAs) or microRNAs (miRNAs) that are complementary to the mRNA of the target gene, leading to its degradation or inhibition of translation.

Question 14

Which of the following is a characteristic of normal cells relative to cancer cells?

Accepted Answer

Normal cells are characterized by differentiation, meaning they have a specific structure and function, unlike cancer cells which may undergo dedifferentiation, losing their specialized features.

Question 15

A benign tumour is usually NOT life-threatening.

Accepted Answer

Benign tumors are generally not life-threatening because they do not invade surrounding tissues or spread to distant parts of the body like malignant (cancerous) tumors do.

Question 16

Many eukaryotic operons are subject to numerous regulatory mechanisms.

Accepted Answer

Eukaryotic genes are typically not organized into operons; this is a feature more common in prokaryotes. Eukaryotic gene regulation occurs at the level of individual genes rather than operons.

Question 17

Acetylation is irreversible.

Accepted Answer

Acetylation, particularly in the context of histone acetylation and deacetylation, is a reversible process. Histone acetyltransferases (HATs) add acetyl groups, while histone deacetylases (HDACs) remove them.

Question 18

What happens to a protein when it is tagged with ubiquitin?

Accepted Answer

Ubiquitination is a process where proteins are tagged with ubiquitin, signaling them for degradation. The tagged proteins are then sent to the proteasome, where they are hydrolyzed into amino acids. This process is crucial for regulating protein levels and removing damaged or misfolded proteins.

Question 19

An operator and transcription unit are called an operon.

Accepted Answer

An operon is a functioning unit of genomic DNA containing a cluster of genes under the control of a single promoter and is regulated by an operator, a sequence that acts as an on/off switch for the genes.

Question 20

Which types of proteins do proto-oncogenes tend to be?

Accepted Answer

Proto-oncogenes often encode for proteins that are involved in signal transduction pathways, including extracellular receptors and protein kinases, which can influence cell growth and division.

Quiz 13: Regulation of Gene Expression