Development of Multicellular Organisms I Flashcards
How do cells have memory?
Retain record of signals their ancestors received during embryonic development.
Remember the environment
Homologous proteins are functionally _________.
Interchangeable
What constitutes the ectoderm?
Cells that cohere to form a sheet of epithelial cells facing external medium
Ectoderm is a precursor of what?
precursor of nervous system and epidermis
What constitutes the endoderm?
Part of the epithelial sheet becomes tucked into the interior
What is the endoderm a precursor of?
Gut, lung, and liver
What forms the mesoderm?
Group of cells move into the space between ectoderm and endoderm and form the mesoderm
What is the mesoderm a precursor of?
Muscles and connective tissue
What is gastrulation?
Transformation of a hollow sphere of cells into a structure with gut
Higher organisms have several homologs of the same gene called what?
gene duplication
What are two classes of proteins most important for development?
Cell adhesion and cell signaling proteins
Gene regulatory proteins
Where are instructions for producing a multicellular animal contained in?
In the non-coding regulatory DNA associated with each gene
DNA contains regulatory elements that serve as binding sites for what/
gene regulatory proteins
What defines the sequential program for development?
Regulatory DNA
Coding sequences in DNA are similar in most organisms but non-coding sequences make one organism what?
different from one another and provide uniqueness
Cell that are fated to develop into a specialized cell type despite changes in environment are called what?
Determined
cells make developmental decisions long before they show any outward signs of differentiation
Cells that can change rapidly due to alterations in environment are called what?
Completely undetermined
Cells that have some attributes of a particular cell type but can change with environment are called what?
Committed
Before acquiring a particular fate, cells express genes that are markers of their location, they are ______.
regionally determined
What is a position specific character of a cell called?
positional value
Cell can become different due to ________ division. These are significant sets of molecules distributed unequally between daughter cells
asymmetric
How can cells born the same can become different?
Due to change in environment after birth
*these molecules then directly or indirectly alter pattern of gene expression between the 2 cells
What are the most important environmental cues to a developing cell?
Signals from neighboring cells
Whats the term?
Induction of a different developmental program in select cells in a homogeneous group leading to altered character
inductive signaling
*few cells closest to the source take on induced character-signal is limited in time and space
What are the types of signal ranges?
Short range: cell-cell contact
Long range: substances that can diffuse through the extracellular medium
How do systems start off?
homogenous and symmetrical
What does the environment impose on the symmetry?
Weak asymmetry
How is asymmetry amplified?
positive feedback
*provides cells with memory
Broken asymmetry is what type of phenomenon?
“all or none”
Morphogen
a long range inductive signal that imposes a pattern on a field of cells. exert graded effects by forming gradients of different concentrations
Each concentration can direct the target cells into a different _________.
developmental pathway
How is the gradient formed?
By localized production of an inducer that diffuses away from its source
Localized production of an inhibitory that diffuses away from its source and block the action of a uniformly distributed inducer
What do morphogens need?
an ‘on’ and ‘off’ system
How are interactions of morphogens blocked?
antagonists or extracellular inhibitors bind to the signal or its receptor
Describe general characteristics of signaling pathways
Conserved family of proteins
Ultimate result of inductive events is change in DNA transcription
Some genes turned ‘on’ others ‘off’
Response depends on spatial and temporal expression of different sets of genes
