Development Flashcards
development
process where an organism undergoes successive changes from a single cell to a mature adult - begins with fertilization
4 stages of development
determination, differentiation, morphogenesis, growth
determination
what type of cell it will become; occurs before distinctive features show
differentiation
processes that give rise to different cell types
morphogenesis
when differentiated cell types get recognized in the multicellular body of the organism
growth
increase in size by cell division or enlargment
most important point of gene regulation during development
transcriptional regulation
different cell types express different
regulatory transcription factors
what causes initial differences in gene expression
location of cell within the organism
stem cell becomes specific cell type when
determination and differentiation have occurred due to activation of different transcription factors
transcription factors in a stem cell determined by
external chemical signals (environment or other cells) and differential gene expression already occurring in the cell
what experiment shows that cell fate is determined early in development
tissue transplantation in early embryo results in normal development, but in late embryo the tissue develops as if it were in its original location
cell potency
the potential/capacity to differentiate
totipotent
cell can become any cell type including more stem cells (early embryo)
pluripotent
cells can develop into most types but can’t become a new embryo
multipotent
can differentiate into limited but related cell types (different connective tissues)
unipotent
can only produce own cell type - most cells in mature organism
whats special about plant cell differentiation
most plant cells can dedifferentiate under certain environmental conditions (can easily be cloned)
what do animal cells require for cloning
cytoplasmic environment of totipotent cell (can fuse extracted nucleus into cytoplasm)
gastrulation in animals
cells move and organize into 3 layers
gastrulation in plants
differential cell expansion
apoptosis
regulated cell death which can lead to developmental abnormalities if disrupted
what do plants have instead of apoptosis
autophagy
differentiation in drosophila begins when
signals tell cells position in time and space (ant/post, dorsal/ventral, right/left planes)
drosophila body plan
head, 3 thoracic segments, 8 abdominal segments
drosophila embryo until the 13th cell division
multinucleated, no cytokineses occurs - molecules can diffuse freely to establish segmentation and developmental axes
morphogen
molecule that exists in a concentration gradient and gives positional info about development
bicoid
protein that leads to development of anterior structures
bicoid mRNA gradient
anterior to posterior
bicoid protein gradient
anterior to posterior
bicoid transcribed
maternally in nurse cells and deposited into eggs before fertilization
nanos
protein that leads to development of posterior structures
nanos mRNA gradient
posterior to anterior
nanos protein gradient
posterior to anterior
nanos transcribed
maternally
hunchback
required for anterior structure formation
hunchback mRNA gradient
diffuse throughout embryo
hunchback protein gradient
anterior to posterior, nanos inhibits translation of hunchback
what method is used to locate mRNA
in situ hybridization
what cellular structure aides in establishment of gradients
microtubules
maternal effects genes
maternally transcribed genes that determine ant/post axis and induces 3 classes of segment genes
gaps genes
maternal or embryo transcribed genes that define broad areas and regulate pair rule genes
pair rule genes
embryonically transcribed genes that refine location of pairs of segments and regulates hox genes and segment polarity genes
hox genes
define segment roles (which structure grows where)
segment polarity genes
determine boundary and anterior/posterior orientation of each segment
how does orientation of hox genes determine development
order of hox genes on chromosome is same order os position of expression in embryo
homeotic mutations
structure formation in wrong segment
what do homeotic mutations indicate
hox genes direct segment identity
evo devo
studies how changes in expression of development genes can lead to phenotypic diversity and formation of new species
tool kit genes
direct pattern formation (ie hox genes)
genetic switches
regulate tool kit genes (DNA regulatory regions, transcription facotrs, signal tranduction molecules)
modularity
independence of developmental processes (one thing can change independently of the whole organism)
heterometry
changing amount of tool kit gene expression
heterochrony
changing time of expression
heterotopy
changing location of expression
Sonic hedgehog and ZRS
ZRS is the enhancer (genetic switch) for morphogen Shh - limb development
