Development Flashcards
processes of development
- cleavage
- gastrulation
- organogenesis
development
a series of progressive changes in form and function that occurs during an organisms life cycle
cleavage
division of cells to form blastula
gastrulation
formation of tissue layers and axis; the blastula is transformed into an embryo with 3 tissue layers and body axes
organogenesis
formation of organs
morphogenesis
cell differentiation and growth to form the complex adult shape
animal hemisphere
contains nucleus of the egg
where nutrients accumulate
the vegetal hemisphere
3 patterns of cleavage
- complete
- incomplete-discoidal
- incomplete-superficial
effect of mitotic spindles on cleavage pattern: 3 types
radial cleavage, spiral cleavage, rotational cleavage
radial cleavage
spindles form at right angles/parallel to animal-vegetal axis
spiral cleavage
spindles at oblique/diagonal angles to animal-vegetal axis
rotational cleavage
first division is parallel to animal-vegetal axis, second division is at right angles
at determination
the cells fate becomes fixed
endoderm (inner layer)
digestive, respiratory and circulatory tracts
ectoderm (outer layer)
epidermis and nervous system
mesoderm (middle layer)
bone, muscle, liver, heart, and blood vessels
blastodisc
the embryo-forming part of an egg - discoidal cleavage
epiblast
embryo
hypoblast
extraembryonic membranes
blastula
an animal embryo at the early stage of development when it is a hollow ball of cells
neurulation
occurs early in organogenesis and begins the formation of the nervous system in vertebrates
somites
produce the vertebrae, ribs, and muscles of the trunk and limbs
neural crest cells produce…
peripheral nerves
development is controlled by
the cytoplasm, genes, external environment
genomic activation
transmission from maternal control to embryo control
cytoplasmic segregation
a factor is unequally distributed in the cytoplasm and ends up in some daughter cells but not others
induction
a factor is secreted by some cells to induce other cells to differentiate
a signal is considered to be a morphogen if…
- it directly affects target cells
2. different concentrations cause different effects
genomic imprinting
some development genes are active only if they come from a sperm, others if they come from an egg
types of segmentation genes
- gap genes
- pair rule genes
- segment polarity genes
- homeotic genes
gap genes
organise large areas along the anterior-posterior axis
pair rule genes
divide the embryo into units of 2 segments each
segment polarity genes
determine segment boundaries
homeotic genes
expressed along the length of the body and determine what the segments will become
apoptosis
programmed cell death, caused by the activation of death genes
clone
an individual that is genetically identical to another individual
4 mechanisms of cloning
- natural - asexual reproduction
- embryo splitting - an early stage embryo is split into two or more genetically identical embryos
- reprogramming somatic cells
- nuclear transfer - removing the DNA from an oocyte (unfertilised egg), and injecting the nucleus which contains the DNA
somatic cell
any cell of a living organism other than reproductive cells
potential uses of cloning
- elite livestock
- disease resistant farming
- developmental research, clones used as controls
- conservation
phenotype of an adult organism results from …
interaction of genes, gene products, and environment
morphological changes result from:
- mutations in the genes that regulate development
- changes in the spatial expression of developmental genes
- changes in temporal expression of developmental genes
gremlin
BMP inhibitor in ducks which prevents BMP4 apoptosis of webbed feet
