Lesson 2 - Concepts in Developmental Biology Flashcards
Concepts in Developmental Biology
- Genomic Equivalence
- Cell Differentiation
- Selective Gene Expression
- Morphogenesis
- Homeotic Genes
- Homeobox Genes
directive influence that determine the course of normal development
preformed
direct initial developmental stages
- maternal genes and
- egg cytoplasm
direct development after cleavage
zygotic genes
- products of the genes
- include the environmental factors which affect development along the way
progressively formed
- each cell in the body has the same genetic material
- all the information necessary to produce a complete gene is present in each cell
genomic equivalence
- the restricition 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 embyro
- 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 cell, but not all –> incomplete embryo
pleuripotency
did the nuclear transfer in amphibians
- M. DiBerardino and
- N. Hoffner Orr.
how was Dolly created
- mammary gland cell nucleus fused with an enucleated oocyte
- implanted in a surrogate mother
- generation of cellular diversity from unicellular zygote
- the process by which a cell becomes different in structure and function
- morphological and functional expression of a portion of the genome
- a cell specialized in one or few synthetic pathways
cell differentiation
what is produced due to cell differentiation
cell diversity
what is the common set of genes shared by different cell types
common set of “housekeeping” gene products
- why there is cell differentiation
- aka differential gene expression
- genes are activated differently dependin on time and space
- depression of certain genes at different times and in different cells
- tunr genes on/off
selective gene expression
selective gene expression is aka what
differential gene expression
where does the activation of genes depend on
- time (phase development)
- space (specific cell)
- 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
when does selective gene amplification happen
during the early diplotene stage of meiosis
what happens in selective gene amplification
nucleoli in germinal vesicle are active in the synthesis of ribosomal RNA
where are the rRNA packaged into during selective gene amplification
about 1500 extra nucleoli beneath the nuclear membrane
- one of the most important varieties of embryonic signal calling
- cells induce or influence adjacent cells to change its behavior
- embryonic tissue induce change to responding tissue which must posses competence to respond to the inducer
embryonic induction
induce change
inductor (embryonic tissue)
responds to inducer
responding tissue
what must the responding tissue posses to respong to the inducer
competence
induces neurulation and axis development
- notochord or
- chordamesoderm
a set of processes that mold the internal and external configuration of an embryo
morphogenesis
- spatial and temporal distribution or organization of differentiated cells
- takes place under tight genetic control
- is the laying down of the morphogenetic blueprint/body plan
- defining the main body axes
- change in form
pattern formation
pattern formation is what
spatial and temporal distribution or organization of differentiated cells
ex of pattern formation
development of arms - upper, lower and fingers
pattern formation takes place under what?
tight genetic control
pattern formation is the laying down of the what
morphogenetic blueprint/body plan
realization of the plan
change in form
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
cell proliferation
cleavage
cell migration
gastrula stage
ex of localized cell death
formation of fingers
- characterized by rapid cell divisions which results to teh increase in number of cells
- mitotic divisions
cell proliferation
- process wherein cells or groups 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 relative great distance
cell migration
ex of cell migration
- invagination
- involution
sheet of cells bends inward
Invagination
tissue sheet rolls inward
involution
process of apoptosis or programmed cell death
- normal cell
- cell shrinkage, chromatin condensation
- membrane blebbing
- nuclear collapse, continued blebbing
- apoptotic body formation
- lysis of apoptotic bodies
process where a cell’s plasma membrane bulges outward and forms bubbles or protrusions
Blebbing
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 idneityt during the early stages of metazoan development
- critical for the proper placement of certain embryonic structures like legs, antennae and eye
homeotic genes
- sequence of 180 base pairs which defines the homeotic genes
- codes for the 61 amino acid protein known as homeodomain
homeobox genes
no. of base pairs in homeobox genes
180 base paris
61 amino acid protein the homeobox codes
homeodomain
where are homeobox genes expressed
highly specific sites and stages of development
- an example of a homeobox gene complex
- are expressed along the craniocaudal axis of the body in the same way as they were arranged in the chromosome
hox genes
where are hox genes expressed
along the craniocaudal axis of teh body in the same was as they are arranged in the chromosome
no of clusters of hox genes in mammals
4 (A-D)
within a given cluster of hox genes, how many subfamilies are there
13 subfamilies or paralogous group of genes
- arranged in strict order along their respective chromosomes
- transcribed in the same order from the 5’ end to the 3’ end
paralogous chromosomes
the homeobox gene is known as what of developmental biology?
Rosetta Stone
- interpret the positional information along the antero-posterior body axis
- both vertebrates and invertebrates have similar types, order of genes in chrom. and pattern of expression
hox genes
diversity of body forms in animals may be due to what?
- verts have 4 hox gene clusters, inverts have 1
- way they interpret the expression differ (time/space)
- gene underwent duplication and divergence which lead to different functions of proteins
- neural crest cells absent in inverts
occurs through discrete and interacting modules
- organisms are contructed of units that are parts of larger units
modularity
allows the formation of redundant structures
duplication
allows the structure to assume a new role
divergence
involves heterochrony and allometry
dissociation
retention of larval traits due
heterochrony
heterochrony is due to what?
- heterochronic expression of certain genes and
- gene mutation in the induction competence system
- different parts of the organism grow at different rates
- may involve altering a target cell’s sensitivity to growth factors or altering the amount of GF produced
allometry
- distinguish between verts from protochordates and inverts
- protochordates have dorsal neural tube and notochord but no real “head”
neural crest cells
responsible for the development of face, skull and branchial arches
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 larval stage
co-option
ex of co-option
- enzyme in liver or crystalin protein in lens
- wings - different forearms with new or diff. functions (flippers, arms)
