cell mov’t - changing patterns of cell adhesion
- cadherins - used in cell-to-cell interactions
- transmembrane proteins that mediate Ca++ binding
- cells w/ similar cadherins tend to go together
- cells w/ most cadherins in interior, cells w/ least cadherins on outside
- integrins - used in cell-to-substrate interactions (involving interactions w/ extracellular matrix)
- used when most of tissue made up of spaces between cells (ECM)
- connects cytoskeleton to the ECM
- can change cytoskeleton growth, way cell secretes materials
induction - cell changes due to interactions w/ another cell
- mosaic development - in Drosophila, where determinants (developmental signals) guide cells on different development paths
- regulative development - in mammals where cell-cell interactions determine development
- proteins used as intercellular signals
- organizers - groups of cells that produce signals for position to other cells
- tells other cells of distance to organizer
- morphogen - signal molecule for determining relative position
determination - cell’s commitment to a certain developmental path
- early cells totipotent, all capable expressing of their genes
- chimera - organism w/ cells from different genetic lines
- differentiation occurs at the end of developmental path, not the same thing as determination
- positional labels - shows cell’s location in embryo, influences how body develops
- cloning of Dolly the sheep on July 5, 1996 from fully-differentiated sheep shows that determination can be reversed
pattern formation - unfolding process that lays down the basic body plan
- currently only fully understood for Drosophila
- sets up anterior/posterior, dorsal/ventral axis
- bicoid protein gradient - determines anterior/posterior axis w/ aid of dynein (protein oskar also plays role for posterior determination)
- accumulation of certain mRNA on 1 side of cell determines dorsal/ventral axis
- polarity found by interactions between follicle cells and oocyte (egg)
- gap genes - map out the subdivision of the embryo
- hunchback mRNA - develops the thorax, cannot by blocked by nanos protein only in the anterior end
- pair-rule genes - alters every other body segment when mutated
- hairy - gene that divides embryo into 7 bands of proteins
- segment polarity genes - subdivides the zones created by hairy
homeotic genes - gives identity to embryonic segments created in pattern formation
- bithorax complex - cluster of genes in 3rd chromosome in Drosophila that affect body parts of thoracic/abdominal segments
- antennapedia complex - cluster of genes that affect body parts of anterior end
- homeobox - sequence of 180 nucleotides that codes for the homeodomain (DNA-binding protein)
- distinguishes portions of genome used for pattern formation
- Hox genes - genes that contain homeoboxes
- 4 copies in vertebrates