Question 1

If you were studying the control of gene expression which begins when processed mRNA reaches the cytoplasm and before there is a protein product,you would be studying

Accepted Answer

Translational control,which determine whether translation begins,occurs in the cytoplasm.The presence of the 5' cap and the length of the 3' poly-A tail can influence the stability of an mRNA transcript and the amount of gene product made.

Question 2

Figure: 
-Which of the following occurs outside of the nucleus in eukaryotic cells?

Accepted Answer

Translational (and post-translational)control occurs in the cytoplasm.

Question 3

Figure: 
-This figure shows the levels at which control of gene expression occurs in eukaryotic cells.What does "B" represent?

Accepted Answer

Refer to Figure 12B.01.

Question 4

Cells from both the hypothalamus and thyroid gland contain the same calcitonin gene,but the calcitonin proteins made in the two tissues differ.What causes the variation in the protein forms?

Accepted Answer

Pre-mRNA alternate splicing during which different introns are removed can cause the particular protein product in cells to be different.Both the hypothalamus and the thyroid gland produce a protein hormone called calcitonin,but the mRNA that leaves the nucleus is not the same in both types of cells.

Question 5

Where in the cell do the translation repressor protein and the proteasome work?

Accepted Answer

Translational control involving the translation repressor protein occurs in the cytoplasm.Post-translational control involving the proteasome occurs in the cytoplasm.

Question 6

What is the function of the translation repressor protein?

Accepted Answer

A translation repressor protein attaches to the beginning of the mRNA,making it impossible for mRNA to bind to a ribosome (and therefore prevents translation of the encoded protein).If the correct signal or chemical binds the translation repressor protein,then the mRNA is released and translation begins.

Question 7

Figure: 
-Which is the correct order of gene expression in eukaryotic cells?

Accepted Answer

The five primary levels of gene expression control are: Chromatin structure,Transcriptional control,Posttranscriptional control,Translational control,Posttranslational control.

Question 8

The control of gene expression which occurs in the nucleus and involves mRNA processing is referred to as:

Accepted Answer

Pre-mRNA processing (splicing)is a form of posttranscriptional control of gene expression.

Question 9

What molecules specifically join with an enzyme to form a RNA-induced silencing complex?

Accepted Answer

Small RNAs are also the source of small interfering RNAs (siRNA)that join with an enzyme to form a RISC (RNA-induced silencing complex).RISC degrades any mRNA that has a base sequence complementary to that in siRNA.

Question 10

Which of the following would,if found,be a new discovery about stimulatory signal transduction pathways for the development of cancer?

Accepted Answer

The stimulatory signal transduction pathway consists of a stimulatory growth factor,the receptor,signaling proteins,and a transcription factor.

Question 11

Which genes code for proteins that stimulate the mitotic cell cycle?

Accepted Answer

Proto-oncogenes code for proteins that promote the cell cycle and inhibit apoptosis.They are often likened to the gas pedal of a car because they keep the cell cycle going.

Question 12

One gene has exons ABCDE.In nerve cells,the mRNA molecules from this gene contain the exons ABC.In muscle cells,the mRNA molecules from this contain BCE.What causes the difference between the mRNA molecules in different tissues?

Accepted Answer

Splicing of a pre-mRNA molecule removes introns and joins exons together.

Question 13

What happens inside a normal cell when a inhibitory growth factor binds to its receptor of the cell membrane?

Accepted Answer

An inhibiting signal transduction pathway ends in stimulation of a tumor suppressor gene,which code for proteins that inhibit the cell cycle and promote apoptosis.

Question 14

Proteins with special tags enter the proteasome and are digested into peptide fragments by a protease.

Accepted Answer

Proteins to be degraded are first tagged with a signaling molecule.Then they enter a proteasome,a large,cylindrical complex that contains a protease.The protease enzymes digest the protein to polypeptide fragments.Refer to Figure 11.7 on page 220.

Question 15

Which type of gene expression control occurs after the protein has been synthesized?

Accepted Answer

Posttranslational control occurs after protein synthesis.The polypeptide product may have to undergo additional changes (modified,portions degraded)before it is biologically functional.

Question 16

Which are cancer-causing genes in mice and humans?

Accepted Answer

Mutation of a proto-oncogene produces an oncogene,which leads to overstimulation of the mitotic cell cycle,cancer and excessive inhibition of apoptosis.

Question 17

Which genes inhibit the cell cycle and promote apoptosis?

Accepted Answer

Tumor suppressor genes code for proteins that inhibit the cell cycle and promote apoptosis.They are often likened to the brakes of a car because they inhibit the cell cycle.

Question 18

What happens inside a normal cell when a stimulatory growth factor binds to its receptor of the cell membrane?

Accepted Answer

A stimulatory signal transduction pathway ends in stimulation of a proto-oncogene,which code for proteins that promote the cell cycle.

Question 19

A newly discovered level of gene expression in vertebrates involves the DNA areas that used to be called "junk DNA".Actually these DNA are encoded into

Accepted Answer

Small RNAs (sRNA)are transcribed from a DNA template located in what use to be called junk DNA because it did not code for protein.The term RNA interference refers to the activities of miRNAs and siRNAs,which are now known to be important for controlling gene expression especially in vertebrates.

Question 20

When insulin is initially synthesized,the polypeptide chain is too long and must have a part cleaved off.What type of regulation of gene expression is this?

Accepted Answer

Post-translational control regulates the activity of proteins.Insulin is only physiologically active after the original polypeptide chain has been cleaved.

Quiz 12: Regulation of Gene Activity