Question

Positional information is important in determining the fate of a cell in a multicellular organism. Animal cells may respond to positional information by a. dividing. b. migrating. c. differentiating. d. undergoing apoptosis. e. doing any of the above.

Short answer

The correct answer is E. Animal cells may respond to positional information by doing any of the activities listed including division, migration, differentiation, or undergoing apoptosis.

Step-by-step solution

Understand Positional Information

Positional information in the context of developmental biology refers to the molecular cues that guide cells in a developing organism to their respective places. This is necessary to organize the cells into tissues and ultimately into an organism's body.

Analysis of the Options

Looking at the options given, it can be deduced that: a. Dividing - Cells can divide in response to positional information to increase the number of cells at a specific location. b. Migrating - Cells can also relocate themselves or migrate in response to positional instructions. c. Differentiating - Positional information can trigger differentiation, the process in which a cell changes from one cell type to another. d. Undergoing apoptosis - Cells can also respond to positional information by undergoing apoptosis, programmed cell death, which is a vital process in shaping structures during development.From these, it is clear that all mentioned activities can be responses of cells to positional information.

Choosing the Correct Option

Given that dividing, migrating, differentiating, and undergoing apoptosis are all activities that might be performed by cells in response to positional information, the most encompassing and therefore correct option is (e) doing any of the above.

Key concepts

Positional Information

Positional information is a fundamental concept in developmental biology, referring to the way cells in a multicellular organism interpret signals to decide their fate. This process is akin to cells receiving a set of instructions about their location and role.

In essence, positional information guides cells to form organized tissues and structures. Cells interpret this information through gradients of soluble molecules, often referred to as morphogens, which are distributed in various concentrations throughout the developing embryo. A classic example is how cells along the anterior-posterior axis in a fruit fly embryo determine their positions to differentiate into head or tail structures.

• Each cell can interpret its position based on morphogen concentration.
• The position then dictates the future development and behavioral response of the cell.

This precise coordination enables complex body plans and functional structures to arise in organisms.

Cell Division

Cell division in response to positional information is crucial during development because it allows the body to form tissues and organs with the correct number of cells in each area.

Cell division involves mitosis, where a parent cell replicates its DNA and divides into two identical daughter cells. For positional information to trigger cell division, signals are often mediated through growth factors and mitogens that indicate when and where cells must multiply.

• Example of triggers include hormonal cues or local concentration gradients of signaling molecules.
• Appropriate cell division in response to these cues prevents overgrowth and ensures tissue integrity.

This regulated growth is essential for creating tissues of the correct size and proportion throughout the organism.

Cell Migration

Cell migration refers to the movement of cells from one location to another in response to positional information. This process is vital for proper development and organization of tissues and organs in an organism.

During development, various chemical signals in the environments, like chemokines, attract cells toward or repel them from particular areas. Migration is orchestrated by cytoskeleton rearrangements, enabling cells to move directionally.

• For example, neural crest cells migrate to form diverse structures, including peripheral nerves and facial bones.
• Misregulated migration can lead to developmental abnormalities or disease states like cancer metastasis.

This intricate process ensures that cells arrive at their destined locations to differentiate further or form complex structures.

Apoptosis

Apoptosis is programmed cell death, and it is another way cells respond to positional information to sculpt and refine tissues and organs.

Unlike traumatic cell death, apoptosis is a controlled process that helps remove cells that are no longer needed. During development, it shapes body structures, like fingers and toes, by removing cells in between them.

• Apoptosis provides a method for eliminating cells that have fulfilled their role or are in excess.
• It also plays a protective role in maintaining tissue homeostasis by removing potentially harmful cells.

Positional information helps dictate where apoptosis occurs, ensuring precise and necessary removal of cells. This balance of cell proliferation and death is what allows an organism to develop correctly while preventing disorder.