Biology Test Biology Developmental Biology & Embryology 2 — Questions and Answers
Question 1: What is embryonic induction?
- The formation of genetically identical twins
- The process of fertilization between egg and sperm
- The process of DNA replication in early cleavage stages
- The ability of one group of cells to signal adjacent cells to adopt a specific developmental fate (Correct answer)
Correct answer: The ability of one group of cells to signal adjacent cells to adopt a specific developmental fate
Embryonic induction occurs when an inducing tissue releases signals that cause a responding tissue to change its developmental trajectory, as in the notochord inducing neural tube formation.
Question 2: Hox genes are critical to animal development primarily because they:
- Determine positional identity along the anterior-posterior body axis by encoding transcription factors (Correct answer)
- Code for all major structural proteins in the cytoskeleton
- Control the rate of mitotic cell division exclusively
- Produce circulating growth hormones that regulate organ size
Correct answer: Determine positional identity along the anterior-posterior body axis by encoding transcription factors
Hox genes encode homeodomain transcription factors that specify segment identity along the anterior-posterior axis; mutations cause homeotic transformations where one body segment adopts the identity of another.
Question 3: What is the role of apoptosis in normal embryonic development?
- It triggers oncogenic transformation in rapidly dividing cells
- It is a purely destructive process with no constructive developmental role
- It sculpts structures by removing specific cells, such as the interdigital webbing between developing fingers (Correct answer)
- It accelerates mitosis by clearing senescent cells from the cell cycle
Correct answer: It sculpts structures by removing specific cells, such as the interdigital webbing between developing fingers
Apoptosis (programmed cell death) is essential for normal morphogenesis; it removes cells between developing digits, shapes the nervous system by eliminating excess neurons, and remodels many organ systems.
Question 4: What are neural crest cells and why are they significant?
- Cells that line the inner surface of the neural tube and produce cerebrospinal fluid
- A highly migratory population derived from the dorsal neural tube that gives rise to diverse cell types including peripheral neurons, melanocytes, and craniofacial cartilage (Correct answer)
- Specialized cells permanently residing in the spinal cord that relay sensory signals
- Cells in the lens of the eye derived from head ectoderm
Correct answer: A highly migratory population derived from the dorsal neural tube that gives rise to diverse cell types including peripheral neurons, melanocytes, and craniofacial cartilage
Neural crest cells are a multipotent, migratory population that delaminate from the dorsal neural tube and travel throughout the embryo, contributing to an extraordinary variety of tissues sometimes called the 'fourth germ layer.'
Question 5: Which term describes the process by which embryonic cells become increasingly structurally and functionally specialized during development?
- Proliferation
- Migration
- Determination
- Differentiation (Correct answer)
Correct answer: Differentiation
Differentiation is the process by which cells acquire distinct molecular, structural, and functional characteristics as they develop from a pluripotent state toward a specialized cell type.
Question 6: What is a morphogen gradient?
- A concentration gradient of a signaling molecule that provides cells with positional information to guide their developmental fate (Correct answer)
- A gradient of available nutrients across different regions of the blastocyst
- The gradient of cardiac output established in the developing heart
- A pH gradient maintained across the plasma membrane of embryonic cells
Correct answer: A concentration gradient of a signaling molecule that provides cells with positional information to guide their developmental fate
Morphogens are signaling molecules that form concentration gradients across a tissue; cells interpret their position in the gradient to adopt different fates, explaining how a field of cells generates diverse cell types.
Question 7: What is organogenesis?
- The scientific study of organ transplantation and rejection
- The process of gamete formation from gonadal stem cells
- The process by which the three primary germ layers differentiate into the specific organs and organ systems of the body (Correct answer)
- The regenerative repair of damaged organs in adult organisms
Correct answer: The process by which the three primary germ layers differentiate into the specific organs and organ systems of the body
Organogenesis is the embryonic stage following gastrulation during which the three germ layers interact and differentiate to form all recognizable organs and organ systems.
