Embryonic Development Quiz

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Questions and Answers

Which term describes the hollow ball of cells formed during early embryonic development?

Blastocyst (correct)

Inner Cell Mass

Trophoblast

Morula

What is the primary role of cytoplasmic determinants in early development?

To influence gene expression by uneven distribution (correct)

To initiate the process of cellular induction

To form the outer layer of the blastocyst

To provide nutrients for the developing embryo

Which component of the blastocyst is the source of embryonic stem cells?

Trophoblast

Morula

Inner Cell Mass (correct)

Cytoplasmic determinants

What process describes the interaction between different cell populations influencing each other's development?

Induction Signup and view all the answers

What is a key characteristic of the morula stage of embryonic development?

It is a solid ball of small cells without enlargement Signup and view all the answers

What is the primary effect of mesoderm on the ectoderm during embryonic development?

It causes the ectoderm to form neural tissue. Signup and view all the answers

Which of the following best describes an inductive event in embryonic development?

A series of events where one tissue influences another's development. Signup and view all the answers

In the context of inductive signaling, what best describes a 'binary' decision?

A cell has a choice between one fate or another, based on signal presence. Signup and view all the answers

How do 'gradient' signals lead to multiple cell fates during embryonic development?

By inducing different fates based on the concentration of a signaling molecule. Signup and view all the answers

What is the key feature of a 'relay' inductive signal in development?

A signal induces a cascade, where cells then signal to their neighbors. Signup and view all the answers

What determines the uniqueness of a cell type?

The specific portions of the genome that the cell expresses. Signup and view all the answers

What process directly leads to the unique function of a cell?

Selective gene transcription, mRNA synthesis, and protein expression. Signup and view all the answers

In any given cell, which genes are actively transcribed?

Genes necessary for basic metabolism and that cell's unique functions. Signup and view all the answers

Which of the following is a characteristic of a terminally differentiated cell, such as a mature keratinocyte?

Cessation of DNA synthesis and stable phenotype Signup and view all the answers

In what manner do reciprocal paracrine interactions influence cell differentiation during epidermal maturation?

Through the exchange of signaling molecules that promote or maintain cellular identity. Signup and view all the answers

What is the primary method used to identify differentiation marker proteins during cell analysis?

RT-PCR and microarray analysis Signup and view all the answers

How does the progression of cancer relate to cell differentiation?

Cancer progression represents a failure of cells to differentiate normally and may result in poor differentiation. Signup and view all the answers

Which of these is an example of a differentiation marker for a hepatocyte?

Albumin Signup and view all the answers

Which of the following cellular components are associated with muscle cells?

Actin and myosin Signup and view all the answers

What is Dicer's role in microRNA (miRNA) processing?

It cuts double-stranded RNA into short segments. Signup and view all the answers

Which of these is NOT a method of cell differentiation control?

Histone modification Signup and view all the answers

What is the primary function of a hematopoietic stem cell?

To generate a variety of blood cells. Signup and view all the answers

What is the role of the hemangioblast?

It gives rise to blood vessels and universal blood stem cells. Signup and view all the answers

What mechanism do miRNAs use to prevent gene expression?

By blocking translation or promoting mRNA degradation. Signup and view all the answers

Which of these correctly pairs a cell type with a major product?

Pancreatic acinar cells - digestive enzymes Signup and view all the answers

What is the immediate precursor to myeloid and lymphoid cells?

Universal blood stem cells. Signup and view all the answers

What is the primary function of red blood cells, which are derived from myeloid precursors?

Transporting oxygen and carbon dioxide Signup and view all the answers

Which type of cell is responsible for initiating blood coagulation?

Platelets Signup and view all the answers

What is the main role of MyoD protein in muscle cell differentiation?

It acts as a transcription factor, binding to enhancers of target genes. Signup and view all the answers

What does it mean for a cell to be 'terminally differentiated'?

The cell's lineage has advanced so far that it is no longer able to differentiate further. Signup and view all the answers

Which cells are directly involved in B and T cell immunity?

Lymphocytes Signup and view all the answers

What is the function of fibrocytes as described?

They produce extracellular matrix, express specific cell markers, and migrate to wound sites. Signup and view all the answers

Which term describes genes like MyoD, myogenin, myf-5, and MRF-4?

Master Regulatory Genes Signup and view all the answers

What type of molecule is MyoD?

A transcription factor Signup and view all the answers

What is the primary mode of action of Tretinoin in cancer therapy?

Activation of all RAR receptors. Signup and view all the answers

Which retinoid is primarily used in the treatment of cutaneous T-cell lymphoma?

Bexarotene Signup and view all the answers

Besides RAR and RXR, which other receptor family can be activated by Acyclic retinoid?

Peroxisome proliferator-activated receptors (PPAR) Signup and view all the answers

What does 'Pan-RAR' activation indicate regarding a retinoid's function?

It activates all subtypes of the retinoic acid receptor. Signup and view all the answers

Which of the following retinoids is used for chemoprevention of hepatocellular carcinoma?

Acyclic retinoid Signup and view all the answers

Which retinoid is primarily used in Kaposi's sarcoma?

Alitretinoin Signup and view all the answers

Which of the following retionoids is described as an RXR agonist?

Bexarotene Signup and view all the answers

What is a therapeutic application associated with fenretidine?

Treatment of breast cancer Signup and view all the answers

Study Notes

Cell Differentiation Control

Cellular differentiation is the process by which cells or parts of an organism become different from one another and from their previous state.
It also describes how cells or tissues acquire the ability to perform specialized functions.
This process is crucial for embryonic development.
The progression from zygote to adult results from cell division, cell differentiation, and morphogenesis.
Cells interact with each other and their environment.
These interactions trigger specific signaling pathways that are either turned 'on' or 'off'.
These pathways mediate proliferation, differentiation and apoptosis.
These processes are vital for development.

Objectives

Understand the cellular differentiation process.
Understand the factors determining and controlling differentiation.
Understand factors determining hematopoiesis and muscle cell differentiation.

Differentiation: Stem Cells

Fertilization of the egg occurs in the oviduct.
The zygote travels to the uterus for implantation.
The zygote divides through mitosis (2-cell, 4-cell, 8-cell embryonic stages, etc.).
The embryo reaches a morula stage (a ball of small cells)
by the end of the first week, the embryo develops into a blastocyst.

Differentiation: Embryonic Stem Cells

The blastocyst is a hollow ball of cells.
It consists of an outer layer of progenitor cells (trophoblast)
inner cell mass (ICM) which are differentiated embryonic stem (ES) cells.
The ICM is the source of embryonic stem cells.
The morula is a mass of cells.
The blastocyst is a hollow ball with an inner cell mass.

Cytoplasmic Determinants and Inductive Signals

An egg's cytoplasm contains RNA, proteins, and other substances unequally distributed.
Cytoplasmic determinants are maternal substances which influence early development.
As the zygote divides (mitosis), cells have different cytoplasmic determinants, leading to various gene expressions.

Cellular Interactions in Development: Induction

Interactions between germ layer cells impact stem cell fate and differentiation pathways.
Induction allows one cell population to influence neighboring cell development, such as mesoderm inducing overlying ectoderm to form neural tissue.
This process involves binary choices (one signal leads to one differentiation path, and vice-versa),
gradient mechanisms that rely on signaling molecule (morphogen) concentration to determine differentiated fates.
cell signal cascades influence neighboring cells' fate.

Cellular Transduction Pathway

Signaling molecules bind to specific receptors on target cells.
This binding initiates a signaling transduction pathway.
The pathway leads to changes in gene expressions.
Signal transduction pathways and signal receptors play crucial roles in differentiation.

Cell Type Specificity

Unique cell characteristics arise from differential gene expressions.

Where Does Differentiation Begin?

Pluripotent stem cells are crucial in the initiation of differentiation.
Totipotent cells, 8-cell embryo, and the blastocyst play a role. (these are also pluripotent stem cells)
Undifferentiated stem cells in vivo or in vitro cultures are involved.

Selective Gene Transcription

Only the genes necessary for a cell's basic metabolism and specialized functions are active in any given cell.
For example, muscle cells express actin and myosin genes,
pancreatic cells express digestive enzyme genes, and
neurons express tubulin and neurotransmitter genes.

Control of Cell Differentiation

Genomic level control.
Transcription and post-transcriptional levels.

Micro-RNAs (miRNA)

miRNA regulates gene expression by targeting mRNA.
Dicer cuts dsRNA short segments.
The single strand (miRNA) associates with protein.
The bound miRNA pairs with complementary mRNA.
This binding prevents gene expression, degrades mRNA, or blocks translation.

Differentiation of Blood Cells

Hematopoiesis is the process of making blood cells from stem cells.
The hematopoietic stem cells produce billions of blood cells to replace aged ones.
Hemangioblasts are stem cells that give rise to blood vessels.
Universal blood stem cells form myeloid and lymphoid precursors.
Myeloid precursors include red blood cells, platelets, and monocytes/granulocytes.
Lymphoid precursors create lymphocytes for immunity. (B and T cells).

Hematopoiesis Regulation

Cytokines and growth factors regulate hematopoiesis, orchestrating diverse progenitor and pluripotent stem cell differentiations.
Key growth factors like FGF, Activin, and BMP-4 regulate pluripotent differentiation.
The cytokine CSF-1 directs GATA-1+ committed progenitors.

Genetic Control of Muscle Cell Differentiation

Myoblasts have master regulatory genes that produce proteins, committing cells to become skeletal muscle (e.g. myoD)
MyoD is a transcription factor binding to enhancers.
MyoD (along with related myogenic factors) initiates muscle-specific protein expression.
These factors are basic helix-loop-helix transcription factors that regulate muscle cell differentiation.

Terminal Differentiation

Cells reach a stage where they cannot progress down any particular lineage.
Examples include neurons, skeletal muscle cells, and keratinocytes.
Fibroblasts are excluded as they can migrate to wounds and express different markers depending on the environment.

Cell Properties

Irreversible differentiation (e.g. mature keratinocytes): DNA synthesis stops.
Reversible differentiation (e.g. hepatocytes): Re-induction of functions like albumin synthesis.

Markers of Differentiation

Markers indicate the mature phenotype of terminally differentiated cells. - Examples include cytokeratins for epithelium, hemoglobin for erythrocytes, albumin for hepatocytes, and so on.

Regulation of Differentiation

Cell-cell interactions (homotypic and heterotypic) influence differentiation through contact, diffusible paracrine factors.
Extracellular matrix and systemic factors (hormones and growth factors).
Oxygen tension affects cells' shape and polarity, differentiation in vitro.

Induction of Differentiation: Cell Interaction

Heterotypic cell interactions and reciprocal paracrine interactions guide differentiation.
Mutual interaction between diverse germ-layer cells promotes differentiation (differentiation).
Paracrine interactions in epidermal maturation.

Diseases Associated with Differentiation

Pulmonary fibrosis results from uncontrolled myofibroblast and fibroblastic activity, leading to excessive collagen deposition.

Differentiation & Diseases

Cancer is a failure of cells differentiating normally.
Poorer differentiation in cancer histology correlates with poorer patient survival.
Tumor cells can be induced to differentiate in tissue culture.

Differentiation & Malignancy

Cancer involves a loss of normal cell differentiation.
Patients with poorly differentiated tumours have a lower survival rate.
Tumour cells can be induced to differentiate in vitro.

Table 17.2. Soluble Inducers of Differentiation

This table lists chemical inducers (e.g. DMSO, sodium butyrate, N-methyl formamide) and their impacts on various cell types during differentiation.

The Clinical Use of Retinoids

Retinoids are used in cancer therapies and prevention.
They impact various aspects of cell behavior including (differentiation), mediated by the nuclear receptor superfamily.

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Description

Test your knowledge on key concepts in embryonic development, including the roles of cytoplasmic determinants, the blastocyst structure, and inductive signaling processes. This quiz covers essential stages from the morula to the specification of cell types.