LESSON 2: CONCEPTS OF DEVELOPMENTAL BIOLOGY Flashcards
each cell in the body has the same genetic material.
therefore, all the information necessary to produce a complete organism.
GENOMIC EQUIVALENCE
the restriction of nuclear potency
ultimate test of whether the nucleus of a differentiated cell has undergone any irreversible functional restriction is to have that nucleus generate every other type of differentiated cell in the body.
AMPHIBIAN CLONING
total capacity of a cell to give rise to a complete embryo
direct the entire development of the organism
true for cells in the early stages of development
totipotency
ability to give rise to several types of cells, but not all —-> incomplete embryo
pleuripotency
mammary gland cell nucleus fused with an enucleated oocyte
Cloning Mammals
generation of cellular diversity
the process by which a cell becomes different in structure & function
morphological & functional expression of a portion of the genome
a cell specialized in one or few synthetic pathways
CELL DIFFERENTIATION
a.k.a. differential gene expression
genes are activated differently depending on time (phase of development) and space (specific cell)
depression of certain genes at different times and in different cells.
SELECTIVE GENE EXPRESSION
transient increase in the number of certain genes without mitosis
an adaptive response for meeting the synthetic requirements of the developing egg
transient increase in the number of certain genes without mitosis
an adaptive response for meeting the synthetic requirements of the developing egg
SELECTIVE GENE AMPLIFICATION
induction of neurulation and axis development by the notochord/ chordamesoderm
EMBRYONIC INDUCTION
a set of processes that mold the internal and external configuration of an embryo
MORPHOGENESIS
Pattern formation of morphogenesis
-spatial and temporal distribution or organization of differentiated cells.
-e.g. development of the arms - upper, lower & fingers
-takes place under tight genetic control
-is the laying down of the morphogenetic blueprint/ body plan
-defining the main body axes
-change in form - is the realization of the plan
Examples of MORPHOGENESIS
-Limb formation
-Establishment of the fundamental axes
-Branching of ducts within the glands
-Formation of the loops and whorls of the fingers (fingerprints)
Six processes involved in morphogenesis
- Cell proliferation
- Cell migration
- Cell aggregation/cell adhesion
- Secretion of extracellular substances
- Change in cell shape
- Localized cell death/apoptosis
characterized by rapid cell divisions which results to the increase in number of cells
mitotic divisions
CELL PROLIFERATION
process wherein cells or group of cells move from one part of the embryo to another
may involve short migrations of individual cell or massive dislocation of groups or sheets of cells over relatively great distance
CELL MIGRATION
Examples of Cell Migration
invagination & involution
Apoptosis (Programmed Cell Death) process:
1.Normal Cell
2.Cells Shrinkage/ Chromatic Condensation
3.Membrane Blebbing
4.Nuclear Collapse/ Continued blebbing
5.Apoptotic body formation
6.Lysis of Apoptotic Bodies
Examples of Apoptosis
-resorption of the tadpole tail
- separation of the digits in the embryonic hand and feet
- selective cell death of neurons that leave specialized connections
set of genes that specify the antero-posterior axis and segment identity during the early stages of metazoan development
critical for the proper placement of certain embryonic structures like legs, antennae and eye.
these genes are expressed in highly specific sites and stages of development.
HOMEOTIC GENES
-sequence of 180 base pairs which defines the Homeotic genes
-Rosetta Stone of developmental biology.
Homeobox
The homeobox codes for the 61 amino acid protein known as _____________
HOMEODOMAIN
many of the Homeobox genes found in_____________ has also been found in vertebrates
Drosophila melanogaster
an example of a Homeobox Gene Complex
these genes are expressed along the craniocaudal axis of the body in the same way as they are arranged in the chromosome.
interpret the positional information along the antero-posterior body axis
both vertebrates & invertebrates have similar types, order of the genes in the chromosomes & pattern of expression
Hox genes
mammalian Hox genes can be arranged into _____________________. Within a given cluster, there are 13 subfamilies or paralogous group of genes
four clusters: Clusters A-D
are arranged in strict order along their respective chromosomes, and transcribed in the same order from the 5’ end to the 3’ end.
paralogous chromosomes
Diversity of body forms in animals may be due to:
-vertebrates have four Hox gene clusters, invertebrates have one
- the way they interpret the expression of genes differ (time/space)
- gene underwent duplication and divergence which lead to different functions of proteins.
- neural crest cells are absent in invertebrates.
occurs thru discrete & interacting modules (units) –Cells –T-O-S
organisms are constructed of units that are parts of larger units.
allows different parts of the body w/o interfering w/ other functions.
Modularity
Examples of Modularity
-Cell lineage (ICM/Trophoblast), morphogenetic fields (eye/limb),
-organ rudiments of vertebrate
-imaginal disc of invertebrates
involves heterochrony & allometry
Dissociation
retention of larval traits (salamander) due to heterochronic expression of certain genes & gene mutation in the induction competence system
Heterochrony
different parts of the organism grow at different rates
may involve altering a target cells’ sensitivity to growth factors or altering the amounts of GF produced.
Allometry
distinguish between vertebrates from protochordates and invertebrates. Protochordates have dorsal NT & notochord but no real “head”
Neural crest cells
responsible for the development of face, skull and branchial arche
Cranial NC
allows for more efficient predation with sensory structures adjacent to the prey-capturing jaws
Cephalization
one gene specify neuron OR antero-posterior axis in the larval stage.
Enzyme in the liver or crystaline protein in the lens
Wings – different forearms with new or diff. functions (flippers, arms )
Co-option
