AP Bio Ch. 18 Study Guide Test Your Knowledge

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Multiple Choice
Identify the choice that best completes the statement or answers the question.

Inducible enzymes

a.	are usually involved in anabolic pathways
b.	are produced when a small molecule inactivates the repressor protein
c.	are produced when an activator protein enhances the attachment of RNA polymerase to the operator
d.	are regulated by inherently inactive repressor molecules
e.	are regulated almost entirely by feedback inhibition

In E. coli, tryptophan switches off the trp operon by

a.	inactivating the repressor protein
b.	inactivating the gene for the first enzyme in the pathway (feedback inhibition)
c.	binding to the repressor and increasing the latter’s affinity for the operator
d.	binding to the operator
e.	binding to the promoter

In the control of gene expression in bacteria, a regulatory gene

a.	has its own promoter
b.	is transcribed continuously
c.	is not contained in the operon it controls
d.	codes for repressor proteins
e.	is or does all of the above

A mutation that renders nonfunctional the product of a regulatory gene for a repressible operon would result in

a.	continous transcription of the genes of the operon
b.	complete blocking of the attachment of RNA polymeerase to the promoter
c.	irreversible binding of the repressor to the operator
d.	no difference in transcription rate when an activator protein was present
e.	negative control of transcription

The control of gene expression is more complex in eukaryotic cells because

a.	DNA is associated with a protein
b.	gene expression differentiates specialized cells
c.	the chromosomes are linear and more numerous
d.	operons are controlled by more than one promoter region
e.	inhibitory or activating molecules may help regulate transcription

DNA methylation of cytosine residues

a.	initiates the acetylation of histones
b.	may be a mechanism of epigenetic inheritance when methylation patterns are repeated in daughter cells
c.	occurs in the proomoter region and enjances binding of RNA polymerase
d.	is a signal for proteasomes to degrade a protein
e.	may be related to the transformation of proto-oncogenes to oncogenes

Which of the following is not true of enhancers?

a.	They may be located thousands of nucleotides upstream from the genes they affect
b.	When bound with activators, they interact with the promoter region and other transcription factors to produce an initiation complex
c.	They may complex with steroid-activated receptor proteins, which selectively activate specific genes
d.	They may coordinate the transcriptioin of enzymes involved in the same metabolic pathway when they contain the same combination of control elements
e.	Each gene may have several enhancers, and each enhancer may be associated with and regulate several genes

Which of the following is not an example of the control of gene expression after transcription?

a.	mRNA stored in the cytoplasm needing activation of translation initiation factors
b.	the length of time mRNA lasts before it is degraded
c.	rRNA genes amplified in multiple copies in the genome
d.	alternative RNA splicing before mRNA leaves the nucleus
e.	splicing or modification of a polypeptide

A eukaryotic gene typically has all of the following associated with it except

a.	a promoter
b.	an operator
c.	enhancers
d.	introns and exons
e.	control elements

10.

Which of the following would you expect to find as part of a receptor protein that binds with a steroid hormone?

a.	a TATA box
b.	a domain that binds to DNA and protein-binding domains
c.	an activated operator region that allows attachment of RNA polymerase
d.	an enhancer sequence located at some distance upstream or downstream from the promoter
e.	transmembrane domains that facilitate the protein’s localization in a plasma membrane

11.

Proteosomes are

a.	complexes of proteins that excise introns
b.	single-stranded RNA molecules complexed with proteins that block translation of or degrade mRNA
c.	small positively charged proteins that form the core of nucleosomes
d.	enormous protein complexes that degrade proteins marked with ubiquitin
e.	complexes of transcription factors whose protein-protein interactions are required for enhancing gene transcription

12.

Which of the following statements explains why a larger portion of the DNA in a eukaryotic cell is transcribed than would be predicted by the number of proteins made by the cell?

a.	multiple enhancer regions are being transcribed to amplify the transcription of protein-coding genes
b.	much of this non-protein-coding RNA functions to regulate the translation or degredation of mRNAs
c.	many of these transcriptions produce double-stranded siRNAs that regulate the transcription of other genes
d.	the additional DNA that is transcribed represents iintrons that are excised from the primary transcript in the production of mRNA
e.	these transcriptions are of noncoding “junk” DNA that is a remnant of mutated protein-coding segments, and the transcripts are degraded by nuclear enzymes

13.

Which of the following is not descriptive of small ncRNAs?

a.	They are thought to have facilitated the evolution of morphological complexity
b.	The inhibition of gene expression by RNA was first observed experimentally and called RNA interference (RNAi)
c.	THe newly discovered piRNAs induce heterochromatin formation, and evidence indicates that they are the most recent ncRNA to have evolved
d.	The regulatory functions of ncRNAs include effects on both transcription and translation
e.	They are often found in “transcription factories” within an interphase nucleus, where they loosen loops of chromatin and enhance transcription of genes on multiple chromosomes

14.

Which of the following descriptions is not part of the process by which miRNA regulates gene expression?

a.	A long miiRNA transcript folds on itself, forming loops called hairpins
b.	An enzyme cuts the hairpins, and dicer trims the ends
c.	One strand is degraded, and the remaining RNA strand associates with proteins
d.	If the miRNA and an mRNA molecule are complementary all along their length, the miRNA is degraded and translation proceeds
e.	If the match between the miRNA and an mRNA is less complete, then translation is blocked

15.

Cytoplasmic determinants are

a.	unevenly distributed cytoplasmic components of an unfertilized egg
b.	often involved in transcriptional regulation
c.	usually separated in the first few mitotic divisions following fertilization
d.	maternal contributions that help to direct the initial stages of development
e.	all of the above

16.

Pattern formation in animals is based on

a.	positional information a cell recieves from gradients of morphogens
b.	the induction of cells by the nurse cells in the mother’s ovary
c.	the packing of chromatin in the nucleus
d.	the differentiation of cells that then migrate together to form tissues and organs
e.	the first few mitotic divisions

17.

What would be that fate of a Drosophila larva that inherits two copies of a mutant bicoid gene (one mutant allele from each heterozygous parent)?

a.	It develops two heads, one at each end of the larva
b.	It develops two tails, one at each end of the larva
c.	It develops normally but, if female, produces mutant larvae that have two tail regions
d.	It develops into an adult with legs growing out of its head
e.	It receives no bicoid mRNA from the nurse cells of its mother

18.

In the following hypothetical embryo, a high concentration of a morphogen called morpho is needed to activate gene P; gene Q is active at or above medium concentrations of morpho; and gene R is expressed so long as any quantitiy of morpho is present. A different morphogen, called phogen, activates gene S and inactivates gene Q when at medium to high concentrations. If morpho and phogen are diffusing from their sites of production at the opposite ends of the embryo, which genes will be expressed in region 2 of this embryo? (Assume a gradient of morphogen concentrations in the three regions, from high at the source, to medium in the middle, and to low at the opposite end.)

a.	genes P, Q, R, and S
b.	genes P, Q, and R
c.	genes Q, and R
d.	genes R and S
e.	gene R

19.

How is the coordinated transcription of genes involved in the same pathway regulated?

a.	The genes are transcribed in one transcription unit, although each gene has its own promoter
b.	The genes are located in the same region of the chromosome, and enzymes acetylate the entire region so that transcription may begin
c.	All the genes resond to the same general transcription factors, although they may respond to different specific trancription factors
d.	A steroid hormone selectively binds to the promoters for all genes
e.	The genes have the same combination of control elements in their enhancers

20.

Which of the following might a proto-oncogene code for?

a.	DNA polymerase
b.	RNA polymerase
c.	receptor protein for growth factors
d.	an enhancer
e.	transcription factors that inhibit cell division genes

21.

A gene can develop into an oncogene when

a.	it is present in more copies than normal
b.	it undergoes a translocation that removes it from its normal control region
c.	a mutation results in a more active or resistant protein
d.	a mutation in a control element increases expression
e.	any of the above occur

22.

A tumor-suppressor gene could cause the onset of cancer if

a.	if both alleles have mutations that decrease the activity of the gene product
b.	only one allele has a mutation that alters the gene product
c.	it is inherited from a parent in mutated form
d.	a proto-oncogene has also become an oncogene
e.	both a and d have occurred

23.

Apoptosis is

a.	a cell suicide program that may be initiated by p53 protein in response to DNA damage
b.	metastasis, or the spread of cancer cells to a new location in the body
c.	the transformation of a normal cell to a cancer cell
d.	the mutation of a G protein into hyperactive form
e.	the transformation of proto-oncogene to an oncogene by a point mutation

24.

Which of the following would most likely account for a family history of colorectal cancer?

a.	a diet that is high in fats and high in fiber
b.	inheritance of one mutated APC allele that regulates cell adhesion and migration
c.	a family history of breast cancer
d.	inheritance of the ras oncogene, which locks the G protein in an active configuration
e.	inheritance of a proto-oncogene