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BIO 250 Exam 3 50 Question with
Solutions A+ Graded.
- In E. coli, how is the regulation of structural genes and regulatory
genes different? - Correct Ans: ✔✔Structural genes are regulated in response to the environmental change (they are not always expressed) while regulatory genes are always expressed. The proteins produced by the regulatory genes are the transcription factors that regulate the structural genes.
what type of biological molecule is an operator, operon, lactose, transcription factor, promoter, and gene (DNA, protein, lipid or
carbohydrage) - Correct Ans: ✔✔operator-DNA
operon-DNA
lactose- carbohydrate
transcription factor- protein
promoter- DNA
gene- DNA
The CAP activator protein and the Lac repressor both control the Lac operon (see Figure Q8-14). Fill out the table below with No expression, Low/Medium expression, or High expression to summarize when the Lac operon will be expressed in each of the three E. coli strains in the table. An example has been done for you.
With high glucose and no lactose, what type of expression will normal e coli cells have, e. coli that have Lacl deleted, and E. coli with
the CAP binding site deleted? - Correct Ans: ✔✔Normal E. coli cells- no expression
E. coli that have Lacl deleted- low/med expression
E coli with the CAP binding site deleted- no expression
The CAP activator protein and the Lac repressor both control the Lac operon (see Figure Q8-14). Fill out the table below with No expression, Low/Medium expression, or High expression to summarize when the Lac operon will be expressed in each of the three E. coli strains in the table. An example has been done for you.
With high glucose and high lactose, what type of expression will normal e coli cells have, e. coli that have Lacl deleted, and E. coli with
the CAP binding site deleted? - Correct Ans: ✔✔normal e coli cells- low/med expression
e. coli that have LacL deleted- low/med expression
E. coli with the CAP binding site deleted- low/med expression
The CAP activator protein and the Lac repressor both control the Lac operon (see Figure Q8-14). Fill out the table below with No expression, Low/Medium expression, or High expression to summarize when the Lac operon will be expressed in each of the three E. coli strains in the table. An example has been done for you.
With no glucose and no lactose, what type of expression will normal e coli cells have, e. coli that have Lacl deleted, and E. coli with the
CAP binding site deleted? - Correct Ans: ✔✔normal e. coli cells- no expression
E. coli that have Lacl deleted- low/med expression
E. coli with CAP binding site deleted- no expression
binds the operator to block transcription of tryptophan biosynthesis genes.
What is glut4? - Correct Ans: ✔✔Transmembrane glucose importer
In the insulin signaling pathway, what is the extracellular signaling
molecule? - Correct Ans: ✔✔insulin
In the insulin signaling pathway, what is the receptor? - Correct Ans:
✔✔insulin receptor
What types of proteins add phosphorylation to other proteins? -
Correct Ans: ✔✔kinases
High glucose levels are present in the blood after eating a sugary meal. Summarize in your own words how glucose is taken up by cells
in response to high glucose levels - Correct Ans: ✔✔Insulin is released by the beta cells in the pancreas into the blood. The insulin then binds to the insulin receptor on target cells, activating the insulin receptor to dimerize and autophosphorylate. This initiates a signaling cascade which activates of the RAB proteins to mobilize Glut4 storage vesicles to fuse with the plasma membrane. This increases the number of Glut4 transporters in the plasma membrane and allows for increased uptake of glucose from the bloodstream.
What is diabetes? - Correct Ans: ✔✔Diabetes is a condition in which blood glucose levels are elevated due to cells not being able to properly uptake glucose from the blood.
This can result either from a lack of production of insulin in response to elevated glucose levels (Type 1 Diabetes) or from a compromised response to insulin within the target cells (Type 2 Diabetes).]
In diabetes patients, insulin signaling does not occur properly. For example, the pancreas may not make enough insulin in response to high blood glucose levels. Hypothesize another problem in the insulin signaling pathway you summarized in Part 1 that could occur in
diabetes - Correct Ans: ✔✔a specific process in the insulin signaling pathway resulting in Glut4 transporter mobilization to the plasma membrane (2 pts) and explain how disruption of that process will result in decreased glucose uptake (2 pts)
True or false: Transcriptional regulators are DNA sequences that can help control gene expression from long distances, up to thousands of
base pairs away - Correct Ans: ✔✔a. False - Transcriptional regulators are proteins; enhancers are DNA sequences that help control gene expression from a long distance.
True or false: Operators are DNA sequences that help control the
expression multiple protein-coding sequences in bacteria. - Correct
Ans: ✔✔True
True or false: Regulatory elements are only found near eukaryotic
genes. - Correct Ans: ✔✔False - operators are also regulatory elements (Elements refers to DNA)
- Which of the following is involved in post-transcriptional control of gene expression?
a. micro-RNAs
b. Histone acetylation
c. Transcriptional activators
d. Nuclear import receptors - Correct Ans: ✔✔micro-RNAs
-microRNAs bind to complementary RNA sequences in messenger RNAs. This causes the RNA-induced silencing complex to degrade the messenger RNA. Since messenger RNA is made by transcription, this is considered post-transcriptional regulation and causes decreased gene expression.
- Compare and contrast the terms enhancer and operator. - Correct
Ans: ✔✔Both terms refer to regulatory elements, or DNA sequences where transcription factors bind. Enhancers are found in eukaryotes and they are regulatory elements that are far away (millions of bases) from the promoter and transcription start site of the target genes. Operator are close to the promoters of operons in prokaryotes.
- What is the difference between heterochromatin and
euchromatin? - Correct Ans: ✔✔Heterochromatin is the chromatin (DNA-protein complex) that is compacted. The nucleosomes (containing histones and DNA) are tightly packed so it is difficult for proteins (transcriptional regulators and/or RNA polymerase) to access the DNA. Genes in heterochromatin are not expressed. Euchromatin is 'open' chromatin and genes are expressed because
the DNA is not as tightly wrapped around histones and the nucleosomes are more spaced out. Euchromatin occurs when histones are acetylated.
- Define endocrine, paracrine, neuronal, and contact-dependent signaling. Order them by the range of the signaling, from shortest distance between the signaling and target cells to the longest distance. Which type of signaling must have a stable extracellular
signaling molecule? - Correct Ans: ✔✔Endocrine signaling is the longest range and must have a stable extracellular signaling molecule to travel through the blood stream. Paracrine is signaling between a target cell and surrounding signaling cells. Neuronal is close range signaling at a synapse between two neurons. Contact-dependent signaling requires two cells to touch. The extracellular signaling molecule is attached to the membrane of the signal cell.
a. Ras is a GTPase, which is an enzyme that is active when it is bound to a small molecule called GTP. Ras mutations are common in certain types of cancers such as lung cancer. Would you predict that these
mutations activate or inhibit Ras? Explain your answer. - Correct
Ans: ✔✔If the mutations cause cancer, they likely increase the pathway (causing more response such as survival and invasion). Therefore, they probably activate Ras to cause the pathway to turn on when the growth factor signal is not present.
A bacteria cell has a mutation the trp repressor that prevents it from binding DNA. Will the tryptophan biosynthesis genes be expressed in
low tryptophan conditions? high tryptophan conditions? - Correct
Ans: ✔✔Yes, Yes
and making the process more complex. Prokaryote gene regulation is not as complex of a process. Another difference is that eukaryotes have both regulations at the transcription level and post- transcriptional regulation, while prokaryotes just have regulation at the transcription level.
Adrenaline (epinephrine) is a derivative of the amino acid tryptophan produced by the adrenal gland that causes increases in blood pressure, heart rate and metabolism. What type of signaling is this? -
Correct Ans: ✔✔endocrine
Insulin signalling communicates to cells that sugar is available in the bloodstream. The insulin gene is expressed in pancreatic beta cells, which release insulin into the blood stream. What type of ligand is
insulin? - Correct Ans: ✔✔protein/peptide
In neuronal development, the cell surface receptors, Notch proteins, bind to their ligands (Delta), which are attached at the cell surface of adjoining cells. How would you classify this type of cell signaling? -
Correct Ans: ✔✔justacrine
A muscle needs to respond quickly to the signal to contract. Is this process more likely to rely on altering protein function or altering
gene expression in a cell to facilitate contraction. Why? - Correct
Ans: ✔✔Since the muscle needs to respond quickly to the signal, altering protein function is the process the cell is most likely going to rely on. This is because proteins are already synthesized, so it can occur within seconds to minutes. Also, the response can happen
directly to the protein without going through the processes of transcription and translation.
How do kinase cascades allow for synthesis of multiple input signals?
- Correct Ans: ✔✔multiple inputs affect individual proteins by integrating points where other signals can be detected. An activity might require multiple phosphorylations at different sites
14-3-3 proteins bind to the phosphorylated PTOV1 to hold PTOV1 in the cytoplasm. When PTOv1 is dephosphorylated, it moves into the nucleus and activates target genes. THis is an example of which of
the following signaling mechanisms? (two mechanisms) - Correct
Ans: ✔✔-kinases and phosphatases
-binding proteins
Why would a signaling pathway need to be regulated? - Correct Ans:
✔✔so there will not be excess waste in the cell. The excess waste can cause toxicity or problematic things to occur in the cell.
What determines where a protein kinase or phosphatase will
perform its enzymatic activity? - Correct Ans: ✔✔Sorting signal sequences determines where a protein kinase or phosphatase will perform its enzymatic activity through protein localization. Also, activation or inactivation by upstream signaling molecules can cause where enzymatic activity occurs.
What are some situations that would require rapid signal
transduction by kinase cascades or second messenger? - Correct
such as transcription and translation. Examples may vary, but can include: RNA polymerase, Ribosomes, Splicing factors, general transcription factors, general translation factors, capping enzyme, histones, polyadenylase, enzymes involved in cellular respiration, etc.
- You are interested in studying the role of a regulatory element proximal to the promoter region of a gene expressed in cardiac smooth muscle cells. In normal cardiac smooth muscle cells, the gene is expressed at high levels. However, in kidney cells, the gene is not expressed at all. You make a luciferase construct to study the function of this regulatory element in each of these two cell types. The construct contains the full promoter along with this element driving expression of the luciferase gene. You mutate this element in that construct and observe the effect it has on expression from that promoter. The normal, non-mutated construct has high luciferase expression in the cardiac smooth muscle cells, but no luciferase expression in the kidney cells. The mutated construct has high luciferase expression in the cardiac smooth muscle cells and high luciferase expression in the kidney cells. From this data, you con -
Correct Ans: ✔✔d. the regulatory element binds a repressor protein in the kidney cells
True or false: histone deacetylases remove lysines from histone tails
- Acetylcholine is released from pre-synaptic cells to initiate muscle cell contraction at neuromuscular junctions. What kind of signaling is this?
a. Endocrine
b. Autocrine
c. Paracrine
d. Neuronal
e. Contact-dependent - Correct Ans: ✔✔neuronal
- Which of the following represents the initial step in a cell signaling pathway?
a. Gene expression changes
b. Phosphorylation of signaling molecules in a kinase cascade
c. Activation of effector molecules
d. Binding of a ligand to its receptor
e. Exchange of GTP for GDP in a small-GTPase - Correct Ans: ✔✔d. binding ofa ligand to its receptor
- Which of the following is true about protein kinases? (Select all that apply.)
a. Protein kinases act as transcription factors to regulate gene expression
b. Protein kinases add phosphate groups to serine, threonine, and/or tyrosine residues on target proteins
c. Protein kinases remove phosphate groups from serine, threonine, and/or tyrosine residues on target proteins
d. Protein kinases can amplify signals by rapidly phosphorylating
many target proteins - Correct Ans: ✔✔b. protein kinases add phosphate groups to serine, threonine, and/or tyrosine residues on target proteins
