biology 111 chapter 18 essay

Which of the following is a protein produced by a regulatory gene?
repressor
A lack of which molecule would result in a cell’s inability to “turn off” genes?
corepressor
Which of the following, when taken up by a cell, binds to a repressor so that the repressor no longer binds to the operator?
inducer
Most repressor proteins are allosteric. Which of the following binds with the repressor to alter its conformation?
inducer
A mutation that inactivates a regulatory gene of a repressible operon in an E. coli cell would result in _____.
continuous transcription of the structural gene controlled by that regulator
The lactose operon is likely to be transcribed when _____.
the cyclic AMP and lactose levels are both high within the cell
Transcription of structural genes in an inducible operon _____.
starts when the pathway’s substrate is present
For a repressible operon to be transcribed, which of the following must occur?
RNA polymerase must bind to the promoter, and the repressor must be inactive.
Altering patterns of gene expression in prokaryotes would most likely serve an organism’s survival by _____.
allowing an organism to adjust to changes in environmental conditions
In positive control of several sugar-metabolism-related operons, the catabolite activator protein (CAP) binds to DNA to stimulate transcription. What causes an increase in CAP activity in stimulating transcription?
a decrease in glucose and an increase in cAMP
There is a mutation in the repressor that results in a molecule known as a super-repressor because it represses the lac operon permanently. Which of these would characterize such a mutant?
It cannot bind to the inducer.
The trp repressor blocks transcription of the trp operon when the repressor _____.
binds to tryptophan
Extracellular glucose inhibits transcription of the lac operon by _____.
reducing the levels of intracellular cAMP
CAP is said to be responsible for positive regulation of the lac operon because _____.
CAP bound to the CAP-binding site increases the frequency of transcription initiation
Imagine that you’ve isolated a yeast mutant that contains histones resistant to acetylation. What phenotype do you predict for this mutant?
The mutant will show low levels of gene expression.
The primary difference between enhancers and promoter-proximal elements is that enhancers _____.
are at considerable distances from the promoter; promoter-proximal elements are close to the promoter
The reason for differences in the sets of proteins expressed in a nerve and a pancreatic cell of the same individual is that nerve and pancreatic cells contain different _____.
sets of regulatory proteins
Gene expression is often assayed by measuring the level of mRNA produced from a gene. If one is interested in knowing the amount of a final active gene product, a potential problem of this method is that it ignores the possibility of _____.
translational control
Not long ago, it was believed that a count of the number of protein-coding genes would provide a count of the number of proteins produced in any given eukaryotic species. This is incorrect, largely due to the discovery of widespread _____.
alternative splicing
One way to detect alternative splicing of transcripts from a given gene is to _____.
compare the sequences of different mRNAs made from the given gene
Which of the following mechanisms is (are) used to coordinate the expression of multiple, related genes in eukaryotic cells?
The genes share a single common enhancer, which allows appropriate activators to turn on their transcription at the same time.
DNA methylation and histone acetylation are examples of _____.
epigenetic phenomena
In eukaryotes, general transcription factors _____
bind to other proteins or to the TATA box
Steroid hormones produce their effects in cells by _____.
binding to intracellular receptors and promoting transcription of specific genes
Which of the following is most likely to have a small protein called ubiquitin attached to it?
a cyclin protein, that usually acts in G1, in a cell that is in G2
The phenomenon in which RNA molecules in a cell are destroyed if they have a sequence complementary to an introduced double-stranded RNA is called _____.
RNA interference
At the beginning of this century there was a general announcement regarding the sequencing of the human genome and the genomes of many other multicellular eukaryotes. Many people were surprised that the number of protein-coding sequences was much smaller than they had expected. Which of the following could account for much of the DNA that is not coding for proteins?
non-protein-coding DNA that is transcribed into several kinds of small RNAs with biological function
Among the newly discovered small noncoding RNAs, one type reestablishes methylation patterns during gamete formation and blocks expression of some transposons. These are known as _____.
piRNA
Which of the following best describes siRNA?
a double-stranded RNA, one of whose strands can complement and inactivate a sequence of mRNA
The fact that plants can be cloned from somatic cells demonstrates that _____.
differentiated cells retain all the genes of the zygote
Your brother has just purchased a new plastic model airplane. He places all the parts on the table in approximately the positions in which they will be located when the model is complete. His actions are analogous to which process in development?
pattern formation
The product of the bicoid gene in Drosophila provides essential information about _____.
the anterior-posterior axis
If a Drosophila female has a homozygous mutation for a maternal effect gene, _____.
all of her offspring will show the mutant phenotype, regardless of their genotype
Mutations in which of the following genes lead to transformations in the identity of entire body parts?
homeotic genes
Which of the following are maternal effect genes that control the orientation of the egg and thus the Drosophila embryo?
egg-polarity genes
The bicoid gene product is normally localized to the anterior end of the embryo. If large amounts of the product were injected into the posterior end as well, which of the following would occur?
Anterior structures would form in both ends of the embryo.
In colorectal cancer, several genes must be mutated for a cell to develop into a cancer cell. Which of the following kinds of genes would you expect to be mutated?
genes involved in control of the cell cycle
A cell is considered to be differentiated when it _____.
produces proteins specific to a particular cell type
When the Bicoid protein is expressed in Drosophila, the embryo is still syncytial (divisions between cells are not yet fully developed). This information helps to explain which observation by Nüsslein-Volhard and Wieschaus?
Bicoid protein diffuses throughout the embryo in a concentration gradient.
The protein of the bicoid gene in Drosophila determines the _____ of the embryo.
anterior-posterior axis
Which of the following types of mutation would convert a proto-oncogene into an oncogene?
a mutation that greatly increases the amount of the proto-oncogene protein
Proto-oncogenes _____.
stimulate normal cell growth and division
The product of the p53 gene _____.
inhibits the cell cycle
Tumor-suppressor genes _____.
encode proteins that help prevent uncontrolled cell growth
BRCA1 and BRCA2 are considered to be tumor-suppressor genes because _____.
their normal products participate in repair of DNA damage
Forms of the Ras protein found in tumors usually cause which of the following?
excessive cell division
A genetic test to detect predisposition to cancer would likely examine the APC gene for involvement in which type(s) of cancer?
colorectal only

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