BIO196 Ch 11-16 Post-Assignments
Which of the following could not result from mutations? A population of animals maintains genetic diversity over many generations. A child is born with achrodroplasic dwarfism, although there is no family history. Chemical treatment of fruit flies results in progeny with white eyes instead of red eyes. A fish in a stream dies from a poison that blocks cellular respiration. A group of skin cells becomes cancerous in a human.
A fish in a stream dies from a poison that blocks cellular respiration.
Binds to a protein and changes its structure.
Alteration of protein function.
Binds to several molecules to attach them together.
Scaffold
A mutation has occurred that prevents UvrA and UvrB from forming a complex. What result will this have on damaged DNA?
The damaged DNA will not be recognized.
Place the steps in the process of targeting a protein to the endoplasmic reticulum in order.
Translation begins. SRP binds to the ER signal sequence. Translation pauses. SRP binds to an SRP receptor in the ER membrane. GTP molecules bound to SRP and the SRP receptor are hydrolyzed. SRP is released. Translation resumes. Polypeptide enters the ER lumen through a channel.
What protein cuts the damaged DNA strand?
UvrC
Which protein has a helicase function?
UvrD
How does glucose affect the lac operon?
When glucose levels are low, cAMP levels are high. cAMP binds to and activates the CAP protein, allowing it to bind to the DNA.
A protein that binds to DNA and activates transcription of some genes is a/an
activator
Function of _____________ can be modulated by binding of small effector molecules, protein-protein interactions, or covalent modifications.
activators and repressors
In the absence of lactose, the lac repressor is
active and can bind to the operator.
CRISPR-Cas is an adaptive defense system in
bacteria
To function as a guide, what must an ncRNA have?
binding sites for several molecules
When in a complex with ________, the CAP protein binds to the CAP site and ________ the expression of the lac operon.
cAMP ; switches on
The ncRNA HOTAIR is associated with what human disease?
cancer
A nucleotide deletion in DNA replication
causes the amino acids inserted after the deletion to be incorrect.
DNA is associated with proteins to form
chromatin
The idea that gene regulation involves multiple factors is called
combinatorial control
Other ncRNA molecules may bind to RNA or DNA due to
complementary base-pairing.
Pieces of bacteriophage DNA are inserted into the spacer region of the ___________ gene.
crispr
Removal of acetyl groups from histones results in a/an ________ in gene expression.
decrease
Increase in gene expression
decrease in compaction of histones acetylation of histone tails removal of histones from a region
At which of the following level(s) can gene expression be regulated in eukaryotes?
destruction of the mRNA initiation of transcription rate of protein synthesis passage of mRNA through the nuclear membrane
If the same bacteriophage infects the bacterium a second time, the _______________ phase begins with production of the _____________ .
expression; pre-crRNA, tracrRNA, and Cas9 protein
T/F: The timing of a mutation during development has negligible effects on the severity of the genetic defect.
false
The lac operon is expressed when
glucose is low and lactose is present.
During interphase, a eukaryotic cell would be expected to
grow, replicate its DNA, and prepare for mitosis.
How does snoRNA function in the process of modifying rRNAs?
guide scaffold
Which of the following is not part of the lac operon?
lacl
If a frameshift mutation causes a stop codon to be inserted into the DNA sequence
the resulting protein will be too short and non-functional.
gene products are required for each phase of the CRISPR-Cas defense system in bacteria --Interference
tracrRNA Cas9 crRNA
gene products are required for each phase of the CRISPR-Cas defense system in bacteria --Expression
tracrRNA Cas9 crRNA pre-crRNA
_____________ base-pairs with the repeat regions and the pre-crRNA is cut into several _____________, each consisting of one repeat region and one spacer.
tracrRNA; crRNA
The most efficient control of eukaryotic gene expression is achieved at the level of
transcription initiation.
What level of regulation do eukaryotes possess that prokaryotes do not?
transport of RNA out of the nucleus
Prevents a cellular process from proceeding
Blocker
gene products are required for each phase of the CRISPR-Cas defense system in bacteria --Adaptation
Cas1 and Cas2
an enzyme that breaks DNA, preventing the bacteriophage from proliferating.
Cas9
HOTAIR role
Chromatin structure and transcription
Which of the following synthesizes the new DNA strand?
DNA polymerase
TERC role
DNA replication
During the cell cycle, why is the change in DNA content from 2n to 4n gradual, but the change from 4n to 2n is abrupt?
DNA replication happens gradually over S phase, whereas cell division happens quickly in M phase.
Recognizes a different ncRNA and inhibits its function
Decoy
In eukaryotic cells, RNA interference plays direct roles in which processes?
Decreasing expression of certain genes
Which of the following is an example of a mutation?
During replication, an A-T base pair in a gene is changed to a G-C base pair.
What statement about regulation of ferritin is true?
Ferritin mRNA is transcribed, but translation is delayed. Ferritin mRNA can only be translated if IRP dissociates from the mRNA. Ferritin mRNA has secondary structure. Ferritin translation is regulated by the concentration of iron in the cytosol.
Cells require certain nutrients to support cell division. There are not sufficient nutrients to support cell division-- checkpoint?
G1
DNA is damaged and DNA content is 2n-- checkpoint?
G1
DNA is damaged and DNA content is 4n-- checkpoint?
G2
DNA replication is incomplete-- checkpoint?
G2
To maintain the integrity of the DNA in the daughter cells, DNA is evaluated before cell division. At which checkpoint would DNA monitoring occur?
G2 checkpoint
CRISPR RNA role
Genome defense
Why is the the ability of glucose to affect transcription of the lac operon an advantage for the bacterial cell?
Glucose is the preferred sugar for the bacteria. If glucose is present, lactose metabolism is suppressed by down-regulating transcription of the lac operon.
Directs one molecule to a particular place in the cell.
Guide
Select the cell cycle impairments that you predict would lead to cancer. Recall that cancer arises from unregulated, repeated cell divisions.
Impaired degradation of cyclins Loss-of-function of important M phase checkpoint proteins Loss-of-function of important G2 phase checkpoint proteins
How is it possible for a single gene to encode more than one polypeptide?
Introns can be removed from pre-mRNA in different combinations.
How does the cell recognize that lactose needs to be metabolized?
Lactose is converted into allolactose, which inhibits the lac repressor.
The cell cycle consists of several checkpoints at which the cycle can be stopped. Which of the following is a function of these checkpoints?
Limiting the amount of daughter cells that might contain genetic abnormalities Preventing the start of mitosis until all chromosomes are fully replicated Making sure chromosomes are correctly attached to the spindle apparatus before nuclear division is complete Ensuring that conditions are favorable for DNA replication and cell division
One chromosome is not attached to the spindle apparatus-- checkpoint?
Metaphase
What would probably NOT increase the accessibility of the DNA for gene transcription?
Methylation of DNA
CCR5 is a cell surface receptor protein of white blood cells that attracts them to specific tissue and organs to elicit an immune response. It is also the receptor to which R5 strains of HIV bind to and enter T cells. Between 5-14% of people from Northern European descent possess an allele known as CCR5-Δ32. In this allele, a 32 base pair section of the gene has been deleted. What phenotype would you predict for people carrying the CCR5-Δ32 allele?
People with CCR5-Δ32 will likely have impaired immune function, but will have resistance to HIV infection.
SRP-RNA role
Protein targeting and secretion
snoRNA role
RNA modification
In the Ames test for mutagenicity, why was rat liver extract included in the control sample?
Rat liver extract contains enzymes that may be necessary for certain mutagens to work. Since it must be added to the experimental sample, it is also added to the control sample.
An RNA molecule with enzymatic activity
Ribozyme
You isolate a cell and wish to determine its current cell cycle phase. You decide to do this by measuring cyclin levels. You find low but detectible levels of G1 cyclin and S cyclin, and no measurable M cyclin. In which cell cycle phase is this cell?
S
Fire and Mello studied the effect of RNAs made from plasmids on gene expression in the nematode C. elegans. As a control, they detected mex-3 mRNA in embryos in which nothing was injected. Why did the control embryos look dark green as shown below?
The cells had high levels of mex-3 mRNA.
A mutation has occurred that has made UvrD non-functional. What result will this have on damaged DNA?
The damaged segment of DNA will be recognized and cut, but it will not be separated from the healthy strand.
A scientist is studying the HOTAIR ncRNA in human cells growing in culture. She identifies a mutation in a cell line that she suspects may affect the function of HOTAIR. The mutation deletes region 1 of the HOTAIR gene that encodes the stem-loop structure at the 3' end of HOTAIR. How is the function of mutant HOTAIR likely to be different from normal HOTAIR?
The mutant HOTAIR will bind to the same target genes as the normal HOTAIR, but it will not inhibit their expression.
If lacO were mutated, what effect would this have on lactose metabolism?
The repressor would not properly bind to the operator, and the lac operon would be over expressed.
What would be the most likely effect of a mutation in a snoRNA that changed the antisense sequence?
The snoRNP would be assembled, but rRNA molecules would not be modified.
How does the cell regulate the initiation of transcription in eukaryotes but not prokaryotes?
Through basal transcription factors
rRNA and tRNA role
Translation
miRNA and siRNA role
Translation and RNA degradation
In the first phase, called _____________, bacteriophage DNA is cut into pieces by a complex consisting of _________ proteins.
adaptation; Cas1 and Cas2
The lac repressor is inactivated by binding to which of the following?
allolactose
T/F: Somatic cell mutations are heritable.
false
The RNA component of telomerase (TERC), has which function(s)?
guide template
The tracrRNA acts as a _____________ for binding of the tracrRNA-crRNA complex to _____________ protein.
guide; Cas9
An activator can increase transcription by attracting a _____________ to the region.
histone acetyltransferase
Addition of (-COCH₃) groups to histone amino terminal tails results in a/an _______ in gene expression.
increase
Decrease in gene expression
increase in compaction of histones removal of acetyl groups from histone tails
The function of all ncRNAs depends on their ability to ______.
interact with other molecules
In the _____________ phase, the spacer region of the crRNA acts as a ____________ to direct the tracrRNA-crRNA-Cas9 complex to bind to the _____________ DNA.
interference; guide; bacteriophage
When a transcription factor interacts with DNA
it forms noncovalent bonds with functional groups on the nitrogenous bases.
The lac repressor binds to what site within the lac operon?
lacO
Which region associated with the lac operon is NOT involved in the binding of RNA polymerase to the DNA?
lacZ
The cell is capable of regulating gene expression in a variety of situations and environments. Valid reasons for a cell to regulate gene expression include its ability to
make additional cells of the same type in response to a demand. synthesize enzymes to metabolize a particular nutrient. execute a specific program of development (e.g. to become a blood cell or immune cell). stop synthesis of a cellular component when there is enough available in the cell.
Which is NOT an example of an ncRNA?
messenger RNA (mRNA)
Modification of bases in DNA, usually resulting in inhibition of transcription, results from
methylation
The function of an ncRNA depends largely on its ability to bind to other
molecules
A __________ is composed of DNA wrapped around an octamer of histone proteins.
nucleosome
A mutation in a gene in the fruit fly Drosophila was found to affect eye color. The protein affected was found to be completely normal in its molecular weight and amino acid sequence, although much less of the protein is made in mutant flies. A reasonable explanation for the change in levels of protein is that the mutation
occurs in the promoter of the gene, within several hundred base pairs of the start of transcription.
RNA polymerase binds to the
promoter
A protein that binds to DNA and blocks activation of a small number of genes is a/an
repressor
To function as a ___________, the structure of an ncRNA molecule must form binding sites for several molecules.
scaffold
Which processes in plants are regulated by ncRNAs?
seed development flowering time development of stomata seedling growth
The pre-crRNA consists of several repeat regions separated by
spacers
The mutations observed by the Lederbergs were
spontaneous
Some ncRNA molecules bind to proteins or small molecules due to
stem-loop structures.
