BIO 325 Test 1

Preformationism

The idea that living things grow from miniature fully formed versions of themselves (specifically within the sperm)

epigenesis

embryos gradually develop characteristics of the organism

somatic mutation theory

carcinogenesis and metastasis results from the proliferation of a cell that acquired mutations

tissue organization field theory

sees cancer as development gone wrong. Interactions between early cancer cells, supporting cells, and tissue environment lead to progressive changes that alter tissues architecture and lead to formation of new niches

homology

share a common evolutionary origin and basic anatomy, but often serve different functions

analogy

different evolutionary origins and anatomy but serve the same function due to similar environmental pressures

choanoflagellates

common ancestor of all animals

coherence

when experimental outcomes from a variety of scientific approaches agree, this supports a hypothesis

embryogenesis

stages of development between fertilization and birth/hatching

pre-embryonic period

weeks 1 and 2, fertilization to gastrulation

embryonic period

weeks 3-8, gastrulation to early organogenesis

fetal period

weeks 9-38, organ maturation, development continues after birth (brain, stem cells, etc.)

fertilization

fusion of haploid gametes reestablishes the diploid genome, activates mechanisms to prevent polyspermy, and restarts the developmental program

cleavage

mitotic cell division without cell growth (total embryo volume stays the same), generates blastomeres, forming a blastula

gastrulation

major reorganization of cells (morphogenesis), three germ layers (ectoderm, mesoderm, endoderm) are formed and the germline is set aside, body axes establishment

ectoderm (outer layer)

germ layer that forms into the epidermis, central nervous system, and neural crest

mesoderm (middle layer)

germ layer that forms into the notochord, bone and muscle, kidney, red blood cells, and facial muscle

dorsal (mesoderm)

mesoderm that forms into notochord

paraxial (mesoderm)

mesoderm that turns into the bone and muscle tissue

intermediate (mesoderm)

mesoderm that turns into the tubule cell of the kidney

lateral (mesoderm)

mesoderm that turns into the red blood cells

head (mesoderm)

mesoderm that turns into the facial muscle

endoderm (internal layer)

germ layer that turns into the digestive tube, pharynx, respiratory tube, gall bladder, pancreas, and liver

organogenesis

organs derived primarily from on germ layer, often requires signals from neighboring tissues, tissue origin of organs is generally conserved across many species

gametogenesis

bipotential diploid germ cell precursors of gametes are reserved during gastrulation, diploid germ cells migrate to the developing gonads, postnatal differentiation of the haploid male and female gametes

phylotypic stage

period in development when the embryos within a phylum have the highest level of shared appearance, time in development when the evolutionarily oldest genes share similar temporal expression patterns

commitment

a transition state between uncommitted and differentiation cells

specification

cells have a fate but not too late to change that fate

autonomous specification

factors within a cell or on the cell surface determine cell fate (can be maternal or zygotic)

conditional specification

factors external to the cell/tissue determine cell fate

determination

cells have a fixed fate, cannot change fates

differentiation

cell has reached its fate

Active genes

permissive histone modifications, open chromatin (euchromatin), RNA polymerase and transcription factors have access to gene

Poised (intermediate state) genes

histone modifications prepare for RNA PII for TF access, has both activators and inhibitors

Repressed (inactive - reversible) genes

repressive DNA or histone modification prevent RNA PII for TF access

Repressed (inactive and harder to reverse)

repressive histone modification, genes inaccessible to RNA PII or TFs

cell transplantation

based on the fate map, cells are removed from a region fated to become one cell type and moved to a region fated to be a different cell type. Host embryos are grown and donor cell type is determined.

extirpation

based on the fate map, cells are removed from a region fated to become one cell type. Embryo is grown and analyzed for a deficit of any cell type

RNA-seq

Embryos are dissociated into single cells > RNA is isolated from individual cells and used to make cDNA with unique barcodes > sequencing is performed and data is annotated based on known cell-type gene expression

• Allows you to develop testable hypotheses about how cell lineages are specified at the molecular level

• Higher throughput than other experimental methods like transplantation and extirpation

BMP4

protein that controls for beak shape/size, as well as controlling apoptosis between the digits

Pax6

gene required for eye development in all animals, a conserved master regulator of eye development, loss of Pax6 function results in loss of eyes

Pitx1

transcription factor that regulates pelvic spine function in 3-spine stickleback, complete loss of function is lethal

Shh (sonic hedgehog)

promotes limb outgrowth

Ubx

protein in insects that is able to repress the Distal-less gene, which inhibits abdominal leg formation (caused by mutation in the protein itself)

Hox gene

Key regulators of axial identity in animals, exist in clusters in the genome, vertebrates have four clusters, more clusters=more diversification of function

collinearity

the arrangement of Hox genes in the genome matches the order in which they are expressed along the anterior-posterior axis, this is preserved in vertebrates

posterior prevalence

the most posterior Hox genes repress the anterior Hox gene expression where they overlap

Hox gene loss of function (Hox gene LOF)

causes an expansion of anterior Hox gene expression and anterior body fates

Hox gene gain of function (Hox gene GOF)

represses anterior hox genes and expands posterior fates

juxtacrine signaling

when two cells are directly interacting with each other or the ECM

paracrine signaling

signaling molecules diffuse from sending cell and act at a distance on other cells

adhesion hypothesis

explains how cells sort and organize during embryonic development, cells with lower surface tension surround cells with higher surface tension

adherens junction

junction created by many cadherin proteins coming together and assumbling

Cadherin

composed of homophilic interactions through the EC1 domain, linked to actin cytoskeleton through their cytoplasmic domains, connected by catenins, calcium sensitive