Development of multicellular systems an der University of Zurich

after gene duplication one homolog sorts with one species and the other one with the other à sequences diverge but they maintain the same activity

à orthologs have homologous origin and also homologous activity

mosaic animals = composed by >2 genotipically different cells 

by method of induction of mitotic recombination --> recombination occurs between sister chromatids in somatic cells before cell division producing 2 cells with different genotypes

drosophila (FLP/FRT System)

mouse (CRE/LoX-P System)

transposable elements can be used to insert in genome eg. Flp (Flipase) binds to Dna sequences caled FRT--> catalyzes chromosomal exchange, when FRT is present on both chromatids it catalyzes transchromosomal exchange. (happens in G2 phase while homologous are pared)

When Flipase is expressed while a tissue grows, there will be 2 population of cells..

cells with no recombination (normal phenotype) and homozygot mutant

when recombination happens early, intere structures are mutated (whole ear) 

later induction in a tissue leads to a clone of cells, that arose from one single ancestral cell

describes the degree of sequence match between compared sequences

(homologous genes can be 100& similar or only 72%)

homologous genes (similar sequences) produced by a gene duplication

à common ancestral gene but have diverged during evolution within the same species à divergence of sequence leads to different activities 

à homologous origin but heterologous activities --> “Division of labour

process through which immature cells become progressively specialised

Genes/ proteins share same activity but not a common origin à have the same function but they lack sufficient similarity to imply that they have a common origin. 

à homologous activity but heterologous origin

molecule that can provide positional information by regulating gene expression in a concentration dependent manner

Tissue that induces and patterns surroundings via induction

site specific

recombination is inducible, highly efficient, (gene encoding recombinase can be put under the control of a tissue specific promoter --> inducible with light, heat)

NO, only effectors can (are regulated by regulators (TF, signalling pathways)

2 individual and gen. different cells that have originated from the same meiotic recombination event

they need to change physically