Question 1

What is the epigenetic landscape model in developmental biology?

Accepted Answer

Conrad Waddington's epigenetic landscape model, published in 1957, describes how cell fate is determined during development. He conceptualized a cell as a marble rolling down a hill, where the path it takes determines its final differentiated state. This model explains how undifferentiated cells receive different signals during development to become distinct cell types.

Question 2

How do morphogens control cell differentiation at different concentrations?

Accepted Answer

Morphogens are signaling molecules that act directly on cells to induce specific responses based on their concentration. Lewis Wolpert's theory proposes that low morphogen concentrations activate one gene, while high concentrations activate different genes. This concentration-dependent mechanism allows cells to interpret molecular signals and differentiate into appropriate cell types during embryonic development.

Question 3

What are the main research questions asked by molecular developmental biologists?

Accepted Answer

Molecular developmental biologists investigate three key areas: identifying molecules that regulate development, such as growth factors; understanding how molecular signals regulate developmental processes, including concentration-dependent effects and paracrine factors; and determining how cells respond to external signals through changes in gene expression or cell morphology.

Question 4

How does immunohistochemistry help visualize protein localization in developing tissues?

Accepted Answer

Immunohistochemistry uses antibodies conjugated to chemical or fluorescent reporters to label specific proteins in tissue sections. Fluorescence microscopy then visualizes these labeled proteins, revealing their localization patterns and potential contributions to cellular structures. This staining technique provides insights into how proteins are distributed during development and tissue formation.

Question 5

What is explant culture and how is it used in developmental research?

Accepted Answer

Explant culture involves removing tissue from its natural growth site and culturing it in controlled laboratory conditions. Researchers can then examine specific growth conditions, such as substrate composition or added growth factors, to study how external stimuli affect developing cells and tissues. This technique allows investigation of developmental mechanisms in a simplified, manipulable environment.

Question 6

How do morpholinos help researchers understand gene function in development?

Accepted Answer

Morpholinos are antisense oligonucleotides injected into developing embryos to reduce the expression of specific genes. By knocking down gene expression, researchers can observe resulting developmental defects and determine the gene's role in normal development. This approach has revealed how genes contribute to structures like the inner ear, where reduced expression causes fewer neurons and hair cells.

Question 7

What does live cell imaging reveal about cell responses during development?

Accepted Answer

Live cell imaging, including time-lapse microscopy, captures cell movements and localization patterns in real time during development. Fluorescently labeled cells can be tracked both in vitro and in vivo, allowing researchers to observe how cells respond to developmental stimuli. This technique reveals dynamic cellular behaviors such as neuron projection growth in response to molecular signals.

An Introduction to Molecular Developmental Biology - Assessment Quiz