Developmental Biology - Lecture 2: Concepts in Development

Vocabulary flashcards covering key terms and definitions from Lecture 2: Concepts in Development.

Cleavage

Division of the fertilized egg into a larger number of cells with no net increase in cell mass before division.

Holoblastic (Complete) Cleavage

Complete cleavage with even yolk distribution and division through the entire embryo; typical in mammals.

Meroblastic (Partial) Cleavage

Cleavage that does not cut through the entire yolk-containing egg; yolk slows/limits division; seen in eggs with heavy yolk (e.g., birds, many insects).

Morphogenesis

Organization of cellular activity in space and time to form structure or pattern; often involves multiple cell behaviors.

Pattern Formation

Process by which cells organize in space and time to form body patterns.

Gastrulation

Dramatic embryo restructuring by cell migrations; forms germ layers and the digestive tract; contrasted with blastula formation.

Germ Layers

Regions of the gastrula that will develop into specific tissue types; three main layers: ectoderm, mesoderm, endoderm.

Ectoderm

Outer germ layer; gives rise to skin and nervous system structures.

Mesoderm

Middle germ layer; gives rise to muscles, skeleton, circulatory system, and other tissues.

Endoderm

Inner germ layer; forms the lining of the gut and associated organs.

Cell Differentiation

Process by which cells become structurally and functionally different from one another; gradual and produces many cell types.

Growth (developmental growth)

Increase in embryo size via more cells, larger cells, and deposition of extracellular materials.

Cell Behaviors

Migrations, shape changes, differential adhesion, division, cell–cell signaling, and cell death that drive development.

Gene Expression

Process by which information from a gene is used to synthesize functional products (often proteins); regulated in development.

Gene Regulation

Control of when and where genes are expressed, via regulatory factors and DNA sequences.

Transcription

Synthesis of RNA from a DNA template.

Translation

Synthesis of proteins from mRNA.

Housekeeping Genes

Genes expressed in all cells for basic cellular function; not development-specific.

Gene Regulatory Networks

Interconnected genes and regulatory factors with feedback that control developmental processes.

Fate

The expected developmental outcome for a cell or region.

Determination

Progress toward a fate; a cell is determined when its fate is fixed by stable internal changes.

Specification

A cell is specified if its fate does not change when placed in a neutral environment.

Fate Map

A map linking regions of an embryo to their differentiated tissue outcomes.

Inductive Interactions

Signals from one tissue influence the development of neighboring cells; can be permissive or instructive.

Morphogen

A signaling molecule that forms a spatial gradient and patterns tissue by eliciting different responses at various concentrations.

Gradient

A spatial concentration gradient of a morphogen across a tissue.

Positional Information

Cell identity is specified by a cell’s position within a morphogen gradient and its threshold responses.

Cytoplasmic Determinants

Molecules unevenly distributed in the cytoplasm and segregated during cell division to influence daughter cell fates.

Asymmetric Cell Division

Division that yields daughter cells with different determinants and fates.

Stem Cells

Undifferentiated cells that can self-renew and produce differentiated progeny.

Multipotent

Stem cells that can differentiate into a limited number of cell types.

Pluripotent

Stem cells that can give rise to most or all cell types of the body (but not extraembryonic tissues).

Totipotent

Cells that can give rise to all cell types, including extraembryonic tissues.

DNA Not a Blueprint

Genome provides a generative program for development—not a full description of the organism; genes interact with signals like morphogens to pattern tissues.