Lecture 30: General Principles Of Development Flashcards
What are the 2 underlying principles of development?
Cell division
Cell differentiation
Since the genome of all cells in an organism is identical, what is the primary controller of development?
Gene expression
What are the 4 cellular processes occurring throughout the development of an embryo?
Cell proliferation
Cell specialization
Cell interaction
Cell movement
What is the significance of the statement: “cells have memory”
Cells retain a record of signals their ancestors received during embryonic development, so current gene expression is a reflection of past AND present environment
T/F Homologous proteins are functionally interchangeable
True
Mouse Engrailed-1 protein has homologous protein in Drosophila called Engrailed. Can be transplanted and works the same
What germ layer forms the precursor of gut, lung, and liver?
Endoderm
What germ layer forms the precursor of nervous system and epidermis?
Ectoderm
What germ layer forms the precursor of muscles and connective tissue?
Mesoderm
The transformation of a hollow sphere of cells into a structure with a gut is called ______________
Gastrulation
Describe the ectoderm
Sheet of epithelial cells facing the external medium
Describe endoderm
Formed when of epithelial sheet becomes tucked into interior
Describe mesoderm
Formed when the group of cells move into the space between ectoderm and endoderm
Compare coding with non-coding regions of DNA
Coding - similar in most organisms
Non-coding - provide uniqueness, contain gene regulatory proteins to control expression
Cells make developmental decisions long before they show any outward signs of differentiation.
Cells that are fated to develop into a specialized cell type despite changes in environment are called ________________
Determined
Cells make developmental decisions long before they show any outward signs of differentiation.
Cells that can change rapidly due to alterations in the environment are called _______________
Completely undetermined
Cells make developmental decisions long before they show any outward signs of differentiation.
Cells that have some attributes of a particular cell type but can change with environment are called ____________
Committed
What is the significance of cellular memory of positional values?
Before acquiring a particular fate, cells express genes that are markers of their location
Cells retain memory of this value –> they are regionally determined
Cells can become different due to what type of division: symmetric or asymmetric?
Asymmetric - significant sets of molecules are distributed unequally between daughter cells
How do sister cells become different when they symmetrically divide?
Environmental influences alter gene expression
Where do most important environmental cues come from with inductive signaling?
Neighboring cells
_____________ ____________ defines the process by which induction of a different developmental program in select cells in a homogenous group leading to altered character
Inductive signaling
What are the 2 types of inductive signaling?
Short range - cell-cell contacts
Long range - substances diffuse through EC medium
A ____________ is a long-range inductive signal that imposes a pattern on a field of cells
Morphogen
What is unique about morphogen signaling?
It exerts graded effects by forming gradients of different concentrations
What are the two components of a morphogen-induced gradient?
Localized production of INDUCER that diffuses away from its source
Localized production of INHIBITOR that diffuses away from its source and blocks action of uniformly distributed inducer
What are the 2 variable components to generating a signal gradient?
Speed of diffusion
Half-life of morphogen
A system starts of homogeneous and symmetrical. The environment imposes a weak asymmetry. What process amplifies this effect?
Positive feedback
True or false: positive feedback mechanisms are reversible with the right external signaling
False: PF is irreversible. Once achieved, external signaling becomes irrelevant
What is the ligand and what is the receptor in Delta Notch signaling?
Delta is a signal TM protein = ligand
Notch = receptor
What two processes are demonstrated by delta notch signaling?
Lateral inhibition and positive feedback
Describe delta notch signaling
When two cells are engaged, part of the notch undergoes proteolysis. A small fragment of the receptor (notch) migrates to the nucleus and initiates gene transcription.
The more active that delta is of one cell, the less active the delta is of the other cell
What are the 3 main factors contributing to diversity in patterns?
Gene duplication
Presence of other signals
Previous experiences of the cell
Signaling pathways originate from a handful of conserved proteins. What is the ultimate result of inductive events?
A change in DNA transcription
Response in signaling pathways depends on __________ and ___________ expression of different sets of genes
Spatial
Temporal
