Exam 3 - Development of multicellular organisms 1 Flashcards
1
Q
What is the general or basic vwie of development of Multicellular organisms?
A
- All organisms begin life as a single cell
- Divide, proliferate, differentiate into different cell types
- Genome of all cells in an organism are identical but the expression of genes is different
- Differential gene expression controls development
2
Q
What is the cell memory?
A
- A record of signals that each cell has from their ancesters recieved during embryonic development
- Genes expressed by cell depend on environment of both past and present
3
Q
True or False the basic machinary for development are interchangeable.
A
True; Homologous proteisnare functionaly interchangable
4
Q
What are the conserved mechanism for development?
A
- Post fertilization, the zygote rapidly divides
- these cells are dependent on food stored in egg by the mother
- Genome is inactive
- Later the genome becomes activated and cells divide and cohere to form a blastula
- hollow filled ball of cells
- Blastula then undergoes massive rearrangemnts to form gastrula
- comprised of three major layers:
- ecto-, meso- . and endo- derms
- comprised of three major layers:
5
Q
What is the name of the process that forms the gastrula and what are the derivatives of three laers formed?
A
- Blastula undergoes Gastrulation
- Transformation of the blastula into a layered structure with a gut
- Ectoderm
- Sheet of epithelial cells facing the external medium
- precursor of the nervous system and epidermis
- becomes tucked in and forms endoderm
- Endoderm
- precursor of gut, lung, and liver
- cells move into space betweem endo and ect
- Mesoderm
- precursoe of muscles and connective tissue
6
Q
What is the structure of the basic animal body plan?
A
7
Q
How similiar are the Fruitfly, nematode, and human and how what may this similiar be due to?
A
- Based on the reconizable homologs
- 50% of genes are shared
- higher organism have several homologs of the same gene
- Gene duplication
- Gene regulatory proteins are the most important for development
8
Q
Why is non-coding regulatory DNA so important?
A
- Instructions for producign a multicellular organism are contained in non coding regulatory DNA.
- Contains regulatory elements that serve as binding sites for gene regulatory proteins
- defines sequential program for development
- Coding sequences in DNA similiar in most organism BUT non coding sequences make one organism different from another and provide uniqueness
9
Q
What is difference between difing a cell as determined, completely undetermined, and committed?
A
- Cells make developmental decisions long before they show any outward sigs of differentiation
- cells that are fated to develope into a specialized cell type despite changes in environment are called determined
- cells that can change rapidly due to alteration in environment are called completely undetermined
- Cels that have some attributes of a particular cell type but can change with environment are called committed
10
Q
What is the positional value of a cell?
A
- Before acquiring a particular fate, cells express genes that are markers of their location ; they are regionally determined
- position specfific character of cell = POSITIONAL VALUE
- cells retain memory of positional value
11
Q
What is asymmetric division?
A
- Cells become different due to asymmetric division
- significant sets of molecules distributed unequally between daughter cells
- Cells born the same can become different due to change in environment after birth (different molecules are induced )
- These molcules then directly or indirectly alter pattern of gene expression between the 2 cells
12
Q
What is inductive signaling?
A
- It is when a signal induces a change in a few cells that is limited to time and space
- Inductive cell signaling occurs when a cell Incorpates different developmental characteristic(s) in homogenous group that leads to an alterations in cells differentiation
- most important environmental cues are signals from neighboring cells
- types of signals
- short range = cell to cell
- Long range : substances that can difuse through the extracellular emdium
13
Q
What is a morphogen?
A
- A long range inductive signal that imposes a pattern on a field of cells
- exerts a gradedt of effects by forming gradients of varying concentration
- Each concentration can direct the target cell in a different developmental pathway
- Gradient is formed by
- localized production of an inducer that diffuses away from its source
- localized production of an inhibitor that diffuese away from its source and blocks the action of a uniformly distributed inducer
- On and Off system
- Antagonists or extracellular inhibtors bind to the signal or its receptor and block interaction
14
Q
what is lateral ingibition and postive feedback?
A
- system starts off homogenous and symmetrical
- environment imposes weak asymmetry
- postivive feedback amplifies effect
- broken asymmetry is all or non phenomenon
- irreversible - once achievved external signal becomes irrevelent
- EX: delta notch signaling
15
Q
What are the underlying factors in diversity of patterns?
A
- Combinatorial control
- response of a cell to a given signal may differ based on presence of other signals (combinations create variety)
- Cell memory
- effect of a given signal depends on previous experiences of the cell (which may have altered its chromatin, regulatory proteins, trascription and RNA)
- Sequential induction
- different signals formed/ secreted in a spatial and temporal manner
16
Q
Example of combinational control and cell memory
A
Example of sequential induction
17
Q
What are the basic characteristics of a signaling pathway?
A
- Handful of conerved family of proteins
- ultimate result of inductive events is change in DNA transcription
- Some genes turned on others turned off
- response depends on spatial and temportal expression of different sets of fenes
