Embryonic development

gastrulation

tissue folding bringing some of the cells into the interior

what does gastrulation create

germ layers

what does the ectoderm become>

stays outside and makes skin, nervous system, sensory cells

what does the mesoderm become

makes connective tissue and muscles

what does the endoderm become

linings of organs and gut

why is the blastula considered adaptable

• splitting the structure in two allows two genetically identcal organisms to develop

• killing one or more cells does not affect development

tissue patterning

guides the spatial organization of the developing organism

developmental timing

ensures processes happen in a certain order; when do genes turn on/off; how do complex layered tissues form

morphogenesis

shaping of tissues; ohw cellsrearrange to change the dimensions of a tissue; how tissues bend and fold into tubes

where does development diverge

coding DNA is very similar between organisms, BUT the regulatory DNA elements are often when divergence occurs

morphogens

molecules that affect cell behavior and identity during development; they are graded in concentration accrossa developing organism, allowing for a graded respnose

different levels of morphogens turn on…

different sets of genes

many organisms need to create ______ boundaries between tissues

sharp

what is engrailed

a transcription factor known for forming these shapr tissue boundaries

how does engrailed work?

1. sets off a feedback loop that ensure neighboring cells act differently

2. activates expression of secreted Hedgehog protein —> this encourages neighboring cells to produce wingless

   1. wingless is secreted and encourages neighboring cells to continue expressing engrailed and hedgehog

what do hox genes specifiy

anterior/posterior axis along the entire animal

what are hox proteins

transcriptino regulators that specifiy the cells according to their position along the body

how are hox genes organized in the genome

located next to eachother in the order they are expressed in thebody axis

what tissue layer of the blastula makes the lining of organs

endoderm

what layer of the gastrula makes the muscles and connective tissue

mesoderm

what drives the earliest stages of development in a fertilized egg?

mRNA and proteins deposited by the mother

maternal effect

the genome of the mother is active usually until gastrulation

morphogen gradients are set up through the….

maternal effect

maternal to zygotic transition

when the zygote begins producing its own gene products

what is the MZT triggered by

increased cell nuclear to cytoplasmic ratio (may be due to a dilution of maternal factors)

what are teh first zygotic genes that are expressed

miRNAs —> function to turn off the maternal RNA; also transcription gactors that can maintain or change the expression of other genes

temporal pattern

a developmental timing process that controls the order in which a single cells expresses genes in a certain sequence for certain lengths of time

convergent extension

a rearrangement in which the tissue narrow in one direction to elongate in the other direction

cell intercalation

when cells rearrange their cell-cell adhesions to switch or exchange with their neighbors

what cellular structures facilitate cell intercalation

cortical actomyosin networks along wiht adherens junctions —> more local myosin accumulation leads to more contraction

neural tube development

a morphogenesis process where the epidermis fold and creates the neural tube

neural tube

precursor to the nervous system