Cell Signaling and Receptors Quiz

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Questions and Answers

Which spontaneous lesion in DNA occurs most frequently in a mammalian cell?

Depyrimidination

Cytosine deamination

Depurination (correct)

Guanine oxidation

Which DNA repair mechanism can introduce DNA sequence errors?

Nonhomologous end joining (correct)

Homologous recombination

Nucleotide excision repair

Base excision repair

Which DNA repair pathway can accurately repair a double-strand break?

Nucleotide excision repair

Base excision repair

Homologous recombination (correct)

Direct chemical reversal

What group of mobile genetic elements is largely responsible for antibiotic resistance in modern bacterial strains?

DNA-only transposons Signup and view all the answers

What main consequence follows DNA chemical damages that occur due to environmental factors?

Prevention of replication mechanisms from functioning properly Signup and view all the answers

What is a primary function of general transcription factors (GTFs) in eukaryotic cells?

Helping RNA polymerases find transcription start sites Signup and view all the answers

Which outcome is associated with alternative splicing?

Creation of multiple proteins from a single region of DNA Signup and view all the answers

What aspect of DNA repair mechanisms varies its accuracy and reliability?

The timing of DNA error occurrences Signup and view all the answers

Which chemical is necessary to disrupt the disulfide bonds for further study of the purified protein?

DTT, a reducing agent Signup and view all the answers

What is the primary fibril protein found in bones, tendons, and skin?

Collagen Signup and view all the answers

How does a cell identify proteins that need to be directed to the proteasome for degradation?

By E2–E3 ligase Signup and view all the answers

Which bonds are critical for the stabilization of secondary structure elements like α helices and β sheets in proteins?

Hydrogen bonds between N—H and C=O groups of the backbone Signup and view all the answers

What conclusion can be drawn from the ability of proteins to renature after denaturation?

Proteins have flexible folding pathways Signup and view all the answers

What is the primary role of hydrogen bonds in protein secondary structures?

They stabilize the folding patterns like α helices Signup and view all the answers

Which of the following statements regarding the proteasome is true?

It is responsible for the degradation of non-functional proteins Signup and view all the answers

Which molecule is not involved in the recognition of proteins for degradation by the proteasome?

Specific phosphatase Signup and view all the answers

What best defines paracrine signaling in cell communication?

A cell targets a nearby cell Signup and view all the answers

Which of the following chemical modifications primarily functions as a molecular switch in cellular signaling?

Phosphorylation Signup and view all the answers

When phospholipase C (PLC) is activated by Gq trimeric GTPase, what is a primary consequence?

Increase in Ca2+ levels, activating protein kinase C Signup and view all the answers

In cell-surface signaling, which two types of receptors are typically represented in simplified diagrams?

Cytokine receptor and TGFβ receptor Signup and view all the answers

Which GTPase is primarily activated by the Epidermal Growth Factor Receptor (EGFR)?

Ras Signup and view all the answers

How does Delta promote gene expression in a neighboring cell according to the Delta-Notch pathway?

Delta activates Notch, which then acts through the JAK-STAT pathway Signup and view all the answers

Which of the following best describes the role of the Gq trimeric GTPase in cell signaling?

It enhances phospholipase C activation to increase calcium levels Signup and view all the answers

What distinguishes paracrine signaling from other types of signaling?

The effects are restricted to neighboring cells Signup and view all the answers

What is the primary purpose of using reverse transcriptase in qRT-PCR?

To convert RNA into complementary DNA Signup and view all the answers

Why is it important to ensure that no DNA is present in the RNA preparation for qRT-PCR?

DNA contamination can lead to inaccurate quantification of mRNA Signup and view all the answers

What role do the chemical dyes play in qPCR and qRT-PCR?

To fluoresce only when bound to double-stranded DNA Signup and view all the answers

How does inositol 1,4,5-trisphosphate (IP3) affect calcium levels in the cell?

It diffuses and opens IP3-gated Ca2+-release channels in the ER. Signup and view all the answers

In a qRT-PCR experiment involving two samples, what does it indicate if the red sample requires fewer PCR cycles to reach half-maximal concentration compared to the blue sample?

The red sample has a higher concentration of mRNA than the blue sample Signup and view all the answers

Which of the following is a key application of qRT-PCR?

To detect changes in mRNA concentration due to mutations Signup and view all the answers

What is the consequence of cGMP phosphodiesterase activation in phototransduction?

Degradation of cGMP resulting in hyperpolarization of photoreceptor cells. Signup and view all the answers

Which statement is true about the quantification process in qPCR?

Quantification relies on a direct relationship between PCR product generation rate and original mRNA concentration Signup and view all the answers

What initiates the cascade of events following cytokine binding to its receptor?

Phosphorylation of tyrosines on cytokine receptors. Signup and view all the answers

What additional feature do mature mRNAs in eukaryotes possess compared to bacterial mRNAs?

They have a 5' cap and a 3' poly-A tail. Signup and view all the answers

What differentiates qPCR from qRT-PCR?

qPCR measures DNA, while qRT-PCR measures RNA Signup and view all the answers

What is a control used in experiments to determine the effect of drug treatment on mRNA concentration?

mRNA from control samples that are not affected by the drug Signup and view all the answers

Which statement about transcription start sites in prokaryotes is correct?

They often coincide with the location of the −35 element. Signup and view all the answers

What role does the α subunit of transducin play in phototransduction?

It activates cGMP phosphodiesterase when bound to GTP. Signup and view all the answers

In the context of exon skipping, what would be the result of such a process on mRNA?

A shorter mRNA that lacks certain exons. Signup and view all the answers

What is the primary action of the JAKs after cytokine binding occurs?

They undergo autophosphorylation and phosphorylate receptors. Signup and view all the answers

What is the probability that each twin daughter from the non-carrier daughter's son and a carrier woman will be a carrier?

50% Signup and view all the answers

If the woman from the family history of a genetic disorder is not a carrier, what is the probability that her child will inherit the disease?

0% Signup and view all the answers

In a scenario where the woman is a carrier and her husband is genotypically normal, what is the chance their son has the disease?

50% Signup and view all the answers

What is the probability that the 30-year-old woman is a heterozygous carrier of the disease-causing mutation, given that both her siblings died from an autosomal recessive disease?

2/3 Signup and view all the answers

What is the probability of the child being affected if the mother is a carrier and father is unaffected, according to the rule of multiplication?

12.5% Signup and view all the answers

What is the inheritance pattern of the disease, considering the mother's family background and the siblings' deaths?

Autosomal recessive Signup and view all the answers

If the maternal uncle had the disorder, what does this indicate about the potential carrier status in the family?

There may be carriers in the family line Signup and view all the answers

What is the significance of the rule of multiplication in determining the probability of having an affected child from a carrier mother?

It allows calculation of independent genetic events Signup and view all the answers

Study Notes

Cell Signaling

Cell signaling is categorized by proximity of signaling molecule to receptor.
Paracrine signaling involves targeting a nearby cell.

Chemical Modifications

Chemical modifications like phosphorylation can act as "molecular switches".

Activation of Phospholipase C (PLC)

Activation of PLC by Gq trimeric GTPase leads to increased intracellular Ca2+ levels.
Elevating intracellular Ca2+ levels activates protein kinase C.

Cell-Surface Receptors

TGFβ receptor and TNF receptor are represented in the diagrams.

EGFR and GTPase

EGFR, a receptor tyrosine kinase (RTK), activates Ras GTPase.

Alzheimer's Disease and Delta-Notch Pathway

Alzheimer's disease is linked to abnormal protein buildup, potentially related to the Delta-Notch pathway.
Delta binding activates Notch, leading to transcriptional activation.

Intracellular Receptors and Steroid Hormones

Nuclear receptors bind specific DNA sequences (upstream of target genes) affecting gene expression in response to steroid hormones.

Calcium Signaling Pathway

Specific signaling pathways lead to increase in intracellular calcium concentrations.

Phototransduction

Phototransduction is a series of events initiated in response to light.

Cell-Mediated Immune Response

Cytokines bind to cytokine receptors, activating JAKs and Tyk2.
This leads to phosphorylation of tyrosine kinase domain and STAT proteins.
STAT proteins enter the nucleus to control gene expression.

Transcription and Translation

The DNA sequence of a region around the 5' end of an Escherichia coli gene is shown.
The first 10 nucleotides of the transcribed mRNA are specified.
Exon skipping in mRNA transcripts results in a specific change in mature mRNA product.
Mature eukaryotic mRNAs contain a 5' cap and a 3' polyA tail.
Eukaryotic ribosomes translate mRNA to build proteins via ribosomes located in cytoplasm.
The start codon of an mRNA usually codes for methionine.

DNA Repair and Transposition

DNA chemical damage occurs naturally and due to environmental factors.
The most frequent spontaneous lesion in mammalian DNA is depurination.
Some DNA repair mechanisms can introduce DNA sequence errors, particularly nonhomologous end joining.
Homologous recombination can accurately repair double-strand breaks caused by ionizing radiation.

Antibiotic Resistance and Mobile Genetic Elements

Nonretroviral retrotransposons play a significant role in antibiotic resistance in modern pathogenic bacteria.
The SARS-CoV-2 virus is composed of RNA strand.
Viral RNA must be transcribed into DNA prior to its translation because the cell machinery cannot immediately translate RNA into proteins.

DNA Lesions and Repair Pathways

Tobacco benzopyrenes and UV light cause bulky nucleotide lesions and various pyrimidine dimers.
Nucleotide excision repair is the primary pathway for repairing these types of lesions.
Damaged DNA triggers the use of backup translesion polymerases during heavy damage to the cell.

SARS-CoV-2 and Reverse Transcription

SARS-CoV-2 is a positive- sense single-stranded RNA virus.
The virus requires reverse transcription to incorporate its genetic material into the host's genome before expressing proteins.

Critical Thinking Questions - DNA Repair

DNA lesions due to various factors like tobacco benzopyrenes or UV light, may cause different kinds of DNA damages.
Different DNA repair mechanisms may be used depending on the type of DNA damage, which can vary in accuracy and reliability.

Critical Thinking Questions - Cancer Genetics

Hereditary conditions, such as Lynch syndrome, are associated with mutations affecting particular genes.
Distinguish between "driver" and "passenger" mutations—driver mutations influence cancer development, while passenger mutations do not.
Point mutations in Ras are frequently linked with cancer.
Abnormal Ras protein function, typically as an activated GTP form, promotes cell growth and cell proliferation, a process needed for cell reproduction.

Protein Structure and Function

A reducing agent (e.g., DTT) is used to break disulfide bonds in proteins.
Collagen is the primary fibril protein in bones, tendons, and skin.
Proteins are recognized for degradation by certain structural/catalytic proteins for destruction.
Disulfide bonds and hydrogen bonds play vital roles in stabilizing the secondary structure of proteins.

Cytoskeleton and Cell Junctions

Kinesin is a motor protein involved in transporting cargo from the cell center to the periphery along the cytoskeleton.
Epidermolysis bullosa is linked to keratin defects.

Cytogenetics Methods

CMA (copy number alteration) screens all 46 chromosomes.
Chromosomal defects such as balanced translocation can be inferred by CMA.

Cell Cycle

Paclitaxel inhibits microtubule depolymerization, arresting the cell cycle at the M phase, where chromosomes are separated and prepare for cell division.
Cyclin B1 is a mitotic regulator whose nuclear localization increases after phosphorylation.
Cell-cycle checkpoints monitor DNA integrity, arresting the cycle if damage is detected.
Certain cell types have inherently higher rates of mitosis.
p53 gene mutations, often involved in cancer, affect cell-cycle regulation.

Cell Death

Pro-apoptotic Bcl-2 family proteins regulate apoptosis in several ways, including activation of nucleases and proteases, generating openings in the mitochondrial membrane.
The release of cytochrome c from mitochondria triggers apoptosis.
Various receptors (e.g., Fas receptors) activate apoptosis pathways.
Necrosis is a pathological cell death caused by significant stress or damage to a cell, resulting in swelling and bursting, rather than the programmed processes of apoptosis.

Genetics of Multifactorial Diseases and GWAS

Genome-wide association studies (GWAS) are commonly used for identifying genetic components of multi-factorial diseases.
GWAS data analysis requires diverse ethnic backgrounds represented in human genome databases.
Genetic variations of alleles (e.g., APOE gene E alleles) have been associated with specific diseases.

DNA Sequencing

Sanger sequencing uses dideoxy nucleotides to terminate DNA synthesis at specific points.
Next-generation sequencing methods (NGS) allow for parallel sequencing of many DNA fragments.
Recombinant DNA is produced by combining DNA fragments from different sources. Techniques such as site-directed mutagenesis can be used to modify gene sequence.

Blots

Southern blots detect DNA fragments.
The northern blot technique detects RNA.
Allele-specific oligonucleotides are specialized probes.
Western blots detect specific proteins.
Enzyme-linked immunosorbent assays (ELISAs) also detect specific proteins.

Additional Notes

Different genetic methodologies can be used to investigate genetic diseases, such as identifying the mode of inheritance from family pedigrees or identifying the type of mutation in a gene associated with disease based on physical characteristics, symptoms or other data.

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Description

Test your knowledge on cell signaling mechanisms and receptor types. This quiz covers topics such as paracrine signaling, the role of phospholipase C, and the Delta-Notch pathway related to Alzheimer's disease. Explore key concepts about G protein-coupled receptors and intracellular signaling.