Mastering Biology Chapter 11

In prokaryotes, a group of closely associated genes with related functions is called _____. A). an operon B). an activator C). RNA polymerase D). constitutive E). a repressor

A). An operon

Your body is composed of a dazzling array of different cell types. Each cell type develops its own unique properties. How does this happen? A). Each cell type is provided with its own specialized set of genes during cell division. B). All cells (with very few exceptions) contain the same set of genes, but the process of gene expression determines which genes are active in each cell. C). The zygote contains one of each of the different cell types. These ancestor cells then divide to produce the diversity of cell types in the adult. D). none of the above

B). All cells (with very few exceptions) contain the same set of genes, but the process of gene expression determines which genes are active in each cell.

Operons are a standard method for gene regulation in _____. A). all organisms B). eukaryotes but not prokaryotes C). prokaryotes but not eukaryotes D). E. coli, but they are rare in other organisms

C). Prokaryotes but not eukaryotes

The lac operon controls expression of three genes that produce lactose-digesting enzymes. What role does lactose play in regulating the lac operon? A). It is not directly involved in gene regulation in this system. B). It turns off the gene that produces the repressor protein, thereby allowing production of the three enzymes. C). It binds to and disables the repressor protein, thereby allowing production of the three enzymes. D). It binds to the promoter region of the operon, thereby allowing RNA polymerase to attach and begin transcription of the three genes.

C). It binds to and disables the repressor protein, thereby allowing production of the three enzymes.

The control of gene expression is more complex in multicellular eukaryotes than in prokaryotes because __________. A). eukaryotic cells are much smaller B). eukaryotic chromosomes have fewer total nucleotides, so each nucleotide sequence must do several jobs C). the genes of eukaryotes provide information for making proteins D). in a multicellular eukaryote, different cells are specialized for different functions E). prokaryotes are restricted to stable environments

D). In a multicelular eukaryote, different cells are specialized for different functions.

Although all of the cells in your body contain a complete set of DNA, different types of cells arise because__________. A). they contain different operons B). they contain different sets of genes C). they contain different chromosomes D). they are differentiated E). different genes are switched on and off in each type of cell

E). Different genes are switched on and off in each type of cell.

Homeotic genes are best described as __________. A). silencers B). proteins that interact with operons in bacteria to control amino acid synthesis C). transcription factors D). the major component of the lac operon E). genes that regulate groups of other genes that determine what body parts will develop in which locations

E). Genes that regulate groups of other genes that determine what body parts will develop in which location.

Regions of noncoding DNA within a gene are called _____. A). coding sections B). transcription factors C). exons D). oncogenes E). introns

E). Introns

Alternative RNA splicing refers to __________. A). combining two or more messenger RNAs into one RNA molecule B). adding a tail to one end of the messenger RNA C). removing different numbers of introns from different RNA transcripts D). adding a cap to one end of the messenger RNA E). splicing different exons out of the same RNA transcripts

E). Splicing different eons out of the same RNA transcripts

Within an operon, repressors _____. A). block gene transcription to RNA by attaching to the operator B). block gene transcription to RNA by attaching to the promoter C). block mRNA translation by attaching to the mRNA for a specific gene D). block gene transcription to RNA by attaching directly to the gene itself

A). Block gene transcription to RNA by attaching to the operator.

In eukaryotes, DNA packing seems to affect gene expression primarily by __________. A). controlling access to DNA B). positioning related genes near each other C). enhancing the recombination of genes D). allowing unpacked genes to be eliminated from the genome E). protecting DNA from mutations

A). Controlling access to DNA

The process by which cells become specialized is called _____. A). differentiation B). alternative RNA splicing C). signal transduction D). divergence E). nuclear transplantation

A). Differentiation

Which of the following would be most likely to lead to cancer? A). mutations in proto-oncogenes and inactivation of a tumor-suppressor gene B). overexpression of both a proto-oncogene and a tumor-suppressor gene C). failure of a proto-oncogene to produce a protein and overexpression of a tumor-suppressor gene D). failure of both a proto-oncogene and a tumor-suppressor gene to produce proteins E). mutations in proto-oncogenes and activation of a tumor-suppressor gene

A). Mutations in proto-oncogenes and inactivation of a tumor-suppressor gene.

All your cells contain proto-oncogenes, which can change into cancer-causing genes. Why do cells possess such potential time bombs? A). Proto-oncogenes are necessary for normal control of cell division. B). Proto-oncogenes are genetic junk that has not yet been eliminated by natural selection. C). Proto-oncogenes protect cells from infection by cancer-causing viruses. D). Cells produce proto-oncogenes as a by-product of mitosis. E). Proto-oncogenes are unavoidable environmental carcinogens.

A). Porto-Oncogenes are necessary for normal control of cell division.

Gene expression involves the flow of information from genes to proteins, which is accomplished via _____ and _____. A). transcription...translation B). transcription...replication C). replication...duplication D). replication...translation E). translation...transcription

A). Transcription...translation

In addition to gene regulation during transcription, other mechanisms regulate gene expression following transcription, including __________. A). breakdown of RNA B). initiation of translation, breakdown of RNA, and protein alteration C). protein alteration D). initiation of translation E). initiation of translation and protein alteration

B). Initiation of translation, breakdown of RNA, and protein alteration.

Cells may use DNA packing and DNA methylation for the long-term inactivation of genes while others remain active. Normally, each cell of a female mammal contains _____ active X chromosome(s). A). three B). one C). four D). five E). two

B). One

The genes that malfunction and cause a cell to become cancerous usually __________. A). control RNA transcription B). regulate cell division C). code for enzymes involved in cellular respiration D). are not present E). are responsible for sex determination

B). Regulate cell division.

It is possible for a cell to make proteins that last for months; hemoglobin in red blood cells is a good example. However, many proteins are not this long-lasting. They may be degraded in days or even hours. What is the advantage of short-lived proteins? A). Most cells have a short life span. B). Short-lived proteins enable the cells to adjust (control) gene expression when this is critical to their well-being. C). Long-lasting proteins are likely to make the cell cancerous. D). Cells lack the raw materials to make most of the proteins they need. E). Most proteins are used only once.

B). Short-lived proteins enable the cells to adjust (control) gene expression when this is critical to their well-being.

To begin the process of gene transcription, RNA polymerase attaches to _____. A). the gene that will be transcribed B). the promoter associated with the target gene C). the operator associated with the target gene D). none of the above

B). The promoter associated with the target gene.