AP Ch Quiz Ch 16 Gene Regulation

"Jumping genes" refers to transposons, which are DNA sequences that can move or "jump" within and between chromosomes. Introns are non-coding regions of DNA, oncogenes are genes that have the potential to cause cancer, retroviruses are a type of RNA virus, and exons are coding regions of DNA. Therefore, the correct answer is transposons.

An enhancer site is located at a distance from the gene it affects. Enhancer sites are regulatory DNA sequences that can increase the transcription of a gene. They can be located upstream, downstream, or even within an intron of the gene they affect. Enhancer sites are not limited to prokaryotes and can be found in both prokaryotes and eukaryotes. They function by binding to specific transcription factors, which then interact with the promoter region of the gene to enhance transcription.

The balance between stimulatory signals and inhibitory signals is crucial in determining the activity of proto-oncogenes and tumor-suppressor genes. Proto-oncogenes can become active and promote cell division and growth when there is an imbalance towards stimulatory signals, leading to the development of cancer. On the other hand, tumor-suppressor genes are responsible for inhibiting cell division and promoting cell death (apoptosis) when there is an imbalance towards inhibitory signals. Therefore, both C and D are correct as an imbalance in stimulatory and inhibitory signals can affect the activity of both proto-oncogenes and tumor-suppressor genes.

Posttranslational control refers to the level of primary control in eukaryotic gene activity that involves modifications and changes to the polypeptide chain after it has been translated from mRNA. These modifications can include processes such as protein folding, addition of chemical groups, cleavage of certain segments, and protein degradation. These modifications are crucial for the protein to become functional and can regulate its activity, stability, and localization within the cell. Therefore, posttranslational control plays a significant role in determining the functionality and regulation of proteins in eukaryotic cells.

The lac operon is a regulatory system found in bacteria that controls the metabolism of lactose. It consists of three structural genes that encode enzymes involved in lactose metabolism. When lactose is present, it binds to the repressor protein, causing it to detach from the operator region of the operon. This allows RNA polymerase to transcribe the structural genes, resulting in the production of the enzymes. Therefore, the statement "It regulates the production of a series of five enzymes" is not correct because the lac operon regulates the production of three enzymes, not five.

An oncogene is a gene that has the potential to cause cancer. Proto-oncogenes are normal genes that regulate cell growth and division. When a proto-oncogene mutates, it becomes an oncogene, which can lead to uncontrolled cell growth and the development of cancer. Therefore, the correct answer is "a mutated form of a proto-oncogene."

Posttranscriptional control involves the processing of early RNA transcripts to mRNA and the regulation of the rate at which mRNA leaves the nucleus. This level of control occurs after transcription has taken place, but before translation occurs. It includes processes such as RNA splicing, capping, polyadenylation, and RNA editing, which modify the mRNA molecule. Additionally, posttranscriptional control can also involve the regulation of mRNA stability and localization within the cell. Overall, posttranscriptional control plays a crucial role in determining the abundance, stability, and localization of mRNA, thereby influencing gene expression in eukaryotic cells.

Translational control refers to the regulation of gene expression at the level of translation, where the mRNA molecule is translated into a protein by ribosomes. This level of control involves the regulation of the life span of the mRNA molecule and its ability to bind to ribosomes. It determines the rate at which proteins are synthesized from the mRNA molecules, thus influencing the overall gene activity.

The trp operon is normally turned on if tryptophan is present, not turned off. Tryptophan acts as the corepressor, not as the activator. The regulator gene product is active by itself, not inactive. Therefore, the statement "Tryptophan binds to the repressor protein and inactivates it" is NOT correct about the trp operon.