Lecture 35 Flashcards
_____ proteins are interchangeable. what does this mean?
homologous
it means that genes are interchangeable ex. fly gene proving to be functional in a mouse (“gene rescue”)
True or false: genes expressed in a cell depend on the environment, both past and present. explain
true
the cell “memory” retains a record of the signals their ancestors received during embryonic development
Define Blastula
a hollow sphere of identical cells
Define gastrula. what is a defining characteristic of this stage?
a collection of cells formed by the invagination of a blastula that has 3 major layers
this is where cells begin to differentiate
Define gastrulation
the transformation of the blastula into a layered structure
The ectoderm is a precursor of what?
nervous system and epidermis
The mesoderm is a precursor of what?
gut, lung, and liver
The endoderm is a precursor of what?
muscles and connective tissue
What is most important for development?
gene regulatory proteins
define gene duplication
it yields several homologs of the same gene (usually in higher organisms)
Where are the instructions for producing a multicellular animal? what do these bind to?
in the non-coding regulatory DNA that is associated with each gene
they bind to regulatory elements which define the sequential program for development
____ _____ in DNA are similar in most organisms but ____ _____ make one organism different from one another.
coding sequences
non-coding sequences
What does it mean when a cell is “determined”?
cells that are fated to develop into a specialized cell type despite changes in the environment
What does it mean when a cell is “committed”?
cells that have some attributes of a particular cell type but can change with the environment
What does it mean when a cell is “completely undetermined”?
cells that can change rapidly due to alterations in the environment
The characters of a cell from genes that are expressed due to it’s location are called what? (what type of cell determination is this?)
positional value
regionally determined
True or false: cells do not retain a memory of their positional value. explain
false
cells DO retain “memory” of genes expressed from their positional value
explain asymmetric division of cells and give an example of this
when significant sets of molecules are distributed unequally between daughter cells
ex. germ cell development
True or False: cells born the same can become different due to environmental changes. explain
true
environmental changes can directly or indirectly alter the pattern of gene expression between the 2 cells
Define inductive signaling
environmental cues from neighboring cells (of a homologous group) that can induce a particular developmental program
State and describe the 2 types of inductive cell signals
Short range: cell-to-cell contacts
Long range: substances that can diffuse through the extracellular medium (Morphogens)
How to morphogens induce their effects on the development of a cell? (describe the 2 ways this may occur)
they exert their effects by forming a “gradient” of different concentrations
Inducers: diffuse away from their source and trigger something
inhibitors: diffuse away from their source and blocks that action of a uniformly distributed inducer
“on off system”
True or false: there are different morphogens that induce cells to differentiate into a particular cell. explain
False.
Cells fate is determined by their location in the gradient of morphogen
ex. lots of morphogen = one cell type and half that amount of morphogen = a different cell type
Explain what it means to create asymmetry between 2 initially identical cells by lateral inhibition and positive feedback
the system begins as homogenous and symmetrical until the environment imposes weak asymmetry
positive feedback amplifies this asymmetrical effect until the 2 cells are very different
