Lecture 15 Review
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What is the outcome of lateral inhibition in cell groups?

  • Cells communicate equally with all neighbors.
  • Cells stop dividing altogether.
  • Some cells predominate over their neighbors. (correct)
  • All cells achieve the same fate.

Which of the following is NOT a mechanism by which cells become different?

  • Inductive signaling
  • Lateral inhibition
  • Uniform cell division (correct)
  • Asymmetric cell division

Which cell signaling pathway is NOT mentioned as a conserved mechanism in animal development?

  • Fibroblast growth factor (FGF) (correct)
  • Transforming growth factor-ß (TGFß)
  • Hedgehog (Hh)
  • Notch

What can result from the same inductive signal applied to different cells?

<p>Diversity in cell responses may occur. (A)</p> Signup and view all the answers

What type of signaling involves communication between neighboring cells for differentiation?

<p>Cell non-autonomous (D)</p> Signup and view all the answers

What are the two phases involved in cell fate commitment?

<p>Specification and determination (B)</p> Signup and view all the answers

Which of the following correctly distinguishes between specification and determination?

<p>Specification does not establish a fixed fate; determination does. (C)</p> Signup and view all the answers

What does the differential gene expression theory explain?

<p>How cells express genes differently to adopt various fates. (B)</p> Signup and view all the answers

Which mechanism can specify cell fate autonomously?

<p>Asymmetric cell divisions (A)</p> Signup and view all the answers

What role does cell-cell communication play in cell fate determination?

<p>It allows cells to acquire different fates non-autonomously. (D)</p> Signup and view all the answers

Which of the following describes induction in the context of cell differentiation?

<p>The method where one cell influences the fate of neighboring cells. (C)</p> Signup and view all the answers

What is the term used for the phenomenon where a group of cells restricts the fate of their neighbors?

<p>Lateral inhibition (A)</p> Signup and view all the answers

Which of the following is NOT a characteristic of totipotent cells?

<p>They are limited to specific fates in differentiation. (A)</p> Signup and view all the answers

What is the initial phase of commitment where cells are reversible in fate determination?

<p>Specification (D)</p> Signup and view all the answers

What does cell fate typically refer to in developmental biology?

<p>The ultimate identity of a cell (C)</p> Signup and view all the answers

Which of the following correctly describes the term 'differential gene expression'?

<p>It dictates cell differentiation. (C)</p> Signup and view all the answers

In an isolation experiment, if a cell expresses a different fate than it would normally, what conclusion can be drawn?

<p>The cell is not specified nor determined. (B)</p> Signup and view all the answers

What does the term 'terminally differentiated' refer to?

<p>A specialized state of a cell (C)</p> Signup and view all the answers

What type of experiment is conducted to test determination by placing cells in a new environment?

<p>In vitro transplantation experiment (A)</p> Signup and view all the answers

What would it indicate if a specified muscle cell changes to muscle despite being placed in a new environment?

<p>It was determined. (A)</p> Signup and view all the answers

What characterizes the cell fate potential according to the concept of step-wise restriction?

<p>Both intrinsic and extrinsic factors influence cell fate. (B)</p> Signup and view all the answers

What defines a cell as determined in developmental biology?

<p>Transplantation does not alter their normal fate. (D)</p> Signup and view all the answers

What is meant by cell fate becoming progressively restricted during development?

<p>Cells lose their ability to become any cell type. (D)</p> Signup and view all the answers

Who demonstrated that a nucleus from a differentiated cell can direct normal development?

<p>John Gurdon (C)</p> Signup and view all the answers

What significant achievement is attributed to Shinya Yamanaka?

<p>Creating induced pluripotent stem cells. (D)</p> Signup and view all the answers

What does the differential gene expression theory suggest regarding somatic cells?

<p>Only a fraction of the genome is expressed in any cell type. (C)</p> Signup and view all the answers

What is the main factor that allows different cell types to exhibit unique characteristics?

<p>Differential gene expression (D)</p> Signup and view all the answers

What was a significant finding from cloning experiments like those conducted with Dolly the sheep?

<p>Adult cells can be used to produce genetically identical organisms. (C)</p> Signup and view all the answers

What happens to genes that are not transcribed in a cell?

<p>They retain potential to be expressed (D)</p> Signup and view all the answers

Which of the following describes an enucleated egg in the context of nuclear transplantation?

<p>An egg cell that has had its nucleus removed. (D)</p> Signup and view all the answers

Which mechanism involves sister cells being born different due to inheritance of cytoplasmic determinants?

<p>Cell autonomous mechanism (D)</p> Signup and view all the answers

What is the role of cell signaling in the context of sister cells becoming different?

<p>It involves non-cell autonomous mechanisms (D)</p> Signup and view all the answers

What type of cell was used by Ian Wilmut to successfully clone Dolly the sheep?

<p>Adult mammary cell (C)</p> Signup and view all the answers

In asymmetric cell division, where are cytoplasmic determinants localized?

<p>Asymmetrically in one daughter cell (B)</p> Signup and view all the answers

What type of mechanism does asymmetric cell division represent?

<p>Cell autonomous mechanism (C)</p> Signup and view all the answers

Which of the following is NOT a way sister cells become different?

<p>Random mutation events (A)</p> Signup and view all the answers

What is the significance of differential gene expression in cellular biology?

<p>It allows for specialization of cell types (A)</p> Signup and view all the answers

What is one mechanism through which sister cells can become different?

<p>Asymmetric division (D)</p> Signup and view all the answers

Which of the following describes a cell nonautonomous mechanism of differentiation?

<p>Inductive signaling (D)</p> Signup and view all the answers

What role do signaling molecules play in cell differentiation?

<p>They relay, amplify, and integrate signals. (D)</p> Signup and view all the answers

Which type of inductive signal results in a consistent outcome, regardless of concentration?

<p>All-or-none signals (D)</p> Signup and view all the answers

How can inductive signals affect cell fate?

<p>They can direct cells to new developmental fates. (A)</p> Signup and view all the answers

Which of the following is an example of a mechanism that involves extracellular signaling?

<p>Lateral inhibition (A)</p> Signup and view all the answers

Which concept best describes how a signaling molecule operates in the extracellular space?

<p>It may alter gene expression in target cells. (A)</p> Signup and view all the answers

What differentiates morphogens from other types of inductive signals?

<p>Morphogens operate in a concentration-dependent manner. (D)</p> Signup and view all the answers

What are the primary functions of signaling molecules during cell development?

<p>Survival, migration, secretion, and metabolism. (D)</p> Signup and view all the answers

Which mechanism is not categorized as cell extrinsic?

<p>Asymmetric division (A)</p> Signup and view all the answers

Flashcards

Cell Differentiation

The process by which cells become specialized, characterized by changes in gene expression and function.

Cell Fate Potential

The potential of a cell to develop into different cell types.

Cell Intrinsic (Cell Autonomous)

A cell's fate is influenced by its internal characteristics, such as its genes and proteins.

Cell Extrinsic (Non-Cell Autonomous)

A cell's fate is influenced by external factors, such as signals from neighboring cells or the environment.

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Specification

The process of commitment to a specific cell fate, but it can be reversed.

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Determination

The irreversible commitment of a cell to a specific fate.

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Isolation Experiment

An experimental method to test cell specification by isolating a cell or tissue and observing its development in a neutral environment.

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In Vitro Transplantation Experiment

An experimental method to test cell determination by transplanting a cell or tissue to a new environment and observing its development.

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Cell Fate Commitment

A cell's commitment to becoming a specific type of cell. It involves two distinct phases: specification and determination. During specification, the cell becomes biased towards a particular fate, but the fate can still be changed. In determination, the fate is permanently committed, and the cell will develop into the specified cell type, even if placed in a different environment.

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Experimental Distinction

A way to distinguish between specification and determination. Researchers can observe if the cell's fate is influenced by its environment, or if it's already locked in.

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Differential Gene Expression Theory

The theory that explains cell differentiation by focusing on the differential expression of genes. Specific genes are activated or deactivated in each cell type, leading to unique protein expression and ultimately, distinct functions.

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Cytoplasmic Determinants

A mechanism where factors within the cytoplasm of a cell influence a daughter cell's fate during cell division. Unequal distribution of these factors leads to different fates for the daughter cells.

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Cell-Cell Communication

The ability of a cell to acquire specific fate based on signals received from neighboring cells. This contrasts with autonomous specification where fate is determined by internal factors.

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Induction

A type of cell-cell communication where one cell directly induces a change in the fate of another cell. This type of communication is often crucial for creating specific tissue patterns.

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Differential Gene Expression

The process by which different cell types express unique sets of genes, resulting in their specialized functions.

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Cell Autonomous Mechanism

A mechanism for cell fate determination where sister cells inherit different cytoplasmic factors during cell division, causing them to become different from the start.

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Asymmetric Cell Division

An example of a cell autonomous mechanism where unequal distribution of regulatory molecules in the cytoplasm results in differing fates for daughter cells.

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Cell Extrinsic Mechanism

A non-cell autonomous mechanism where cell fate is determined by interactions between cells.

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Cell Signaling

A process involving communication between cells that plays a critical role in cell differentiation.

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PARs

A group of proteins involved in asymmetric cell division in the nematode C. elegans.

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MEX-5

A protein involved in asymmetric cell division in the nematode C. elegans, it is involved in the localization of other regulatory molecules.

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Cell Determination

A cell is determined if its fate is fixed and it will develop into a specific cell type, even when moved to a different environment in the embryo.

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In Vivo Test for Determination

A test where a cell is moved to a new location in the embryo to see if it develops according to its original fate or adopts the new location's fate.

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Commitment to a Particular Fate

A series of steps leading to a cell becoming increasingly specialized. Each step is irreversible, meaning the cell cannot go back to a previous stage.

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Nuclear Transplantation Experiment

The nucleus of a differentiated cell can still direct normal development when transplanted into an enucleated egg. This shows that the genome remains complete and hasn't been altered during development.

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Gurdon's Experiment (1962)

The very first animal cloning experiment using a nucleus from a differentiated tadpole skin cell.

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Pluripotent Cells

Cells that have the potential to develop into any cell type in the body.

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Yamanaka Factors

Factors discovered by Yamanaka that can reprogram mature cells to become pluripotent cells.

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Lateral Inhibition

A type of cell communication where a cell inhibits the activity of its neighboring cells, leading to a stronger response in the cell that is not inhibited.

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Notch Signaling Pathway

A signaling pathway that determines the fate of a cell by initiating a cascade of events that lead to specific gene expression.

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Hedgehog (Hh) Signaling Pathway

A signaling molecule that acts as a morphogen, creating a concentration gradient that influences the development of neighboring cells.

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Inductive Signaling

A type of cell-cell signaling where one cell sends a signal to another cell, influencing its development and function.

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Transforming Growth Factor-ß (TGFß) Signaling Pathway

A signaling pathway that involves a family of proteins that regulate cell growth, differentiation, and apoptosis.

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Cell-autonomous differentiation

Sister cells become different due to internal factors within the cell, such as unequal distribution of molecules during cell division.

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Cell-nonautonomous differentiation

Sister cells become different due to external signals from neighboring cells or the environment.

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Morphogen

A signaling molecule that influences cell fate in a gradient, with different concentrations triggering different fates.

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Asymmetric division

The process of cell division where one parent cell divides into two daughter cells with different fates.

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Extracellular signaling molecule

A signaling molecule that binds to a receptor on a cell's surface, initiating a signal transduction pathway.

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Cell-surface receptor

A protein on a cell's surface that binds to a signaling molecule, triggering a signal transduction pathway.

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Signal transduction pathway

A series of molecular events within a cell that transmit a signal from the cell surface to the nucleus or other cellular components.

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Effector

A molecule or process that is activated by a signal transduction pathway, resulting in a change in cell behavior.

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Study Notes

Cell Fate Commitment

  • Cell fate commitment involves two phases: specification and determination.
  • Specification is a reversible commitment to a particular fate.
  • Determination is an irreversible commitment to a particular fate.

Testing Specification

  • An isolation experiment can test for cell specification.
  • If a cell expresses a different fate than normal in isolation, it is not specified.
  • If a cell expresses its normal fate, it is specified.

Testing Determination

  • In vitro transplantation experiments can test for cell determination.
  • If a cell expresses its normal fate in a new environment, it is determined.
  • If a cell does not express its normal fate in a new environment, it is not determined.

In Vivo Test for Determination

  • Cells are determined if their fate does not change when transplanted to a new position in the embryo.

Commitment to a Particular Fate is Progressive

  • Each step of commitment is irreversible.
  • Cell fate becomes increasingly restricted during development.

Differential Gene Expression Theory

  • The genome remains constant in all somatic cells.
  • Only a small portion of the genome is expressed in any given cell type.
  • Different cell types express different gene groups, resulting in unique cellular characteristics.
  • Unused genes that are not transcribed are retained.

Differential Gene Expression Makes Cells Different

  • Specific transcription regulators control the expression of certain genes.
  • Regulatory modules determine gene expression patterns, leading to cell differentiation.

Two Ways of Making Sister Cells Different

  • Cell autonomous: Asymmetric division causes sister cells to be different due to cytoplasmic determinants.
  • Cell nonautonomous: Cell signalling or inductive signalling leads to sister cells becoming different from differences acting on and/or between them.

Asymmetric Cell Division

  • Cytoplasmic determinants become asymmetrically localized.
  • Cytoplasmic determinants are inherited by one daughter cell.

Examples of Asymmetric Cell Division

  • The first division in C. elegans produces different cells.

Cell Non-Autonomous Mechanisms

  • Inductive signaling and lateral inhibition.

Inductive Signaling

  • Some inductive signals function in an all-or-none manner.
  • Other signals function in a concentration-dependent manner.
  • Morphogens are diffusible molecules with varying concentrations that produce specific cellular responses.

Morphogen Gradients

  • Morphogens are secreted from a source.
  • They form concentration gradients with the highest concentration near the source.
  • Cells respond to morphogen concentrations, leading to a reproducible pattern of differentiation.
  • Example Shh (Sonic Hedgehog) in the chick limb bud.
  • Inappropriate morphogen expression can lead to extra digit formation.

Cellular Differentiation and Tissue Asymmetries

  • Equivalent cells can adopt different fates due to cell-cell interactions and lateral inhibition.

Lateral Inhibition

  • Equivalent cells can adopt different fates.
  • Cells compete by inhibiting neighbors and one cell predominates. This mechanism directs the development of a set pattern (e.g. fly bristles).

Cell-Cell Communication in Animal Development

  • Cell-cell signaling involves a small number of conserved pathways.
  • Important pathways include TGFβ, Wnt, Hedgehog, Notch, and RTKs.
  • Sequential inductions can direct and control the differentiation hierarchy.
  • Combinations of signals can result in diverse cellular responses.

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