Other factors affecting expression
Mosaicism
- when all the cells in the body do not have the same genotype
- can affect either germline or somatic tissues
- in germline can cause a spontaneous mutation in offspring
- human mutation rates 1/107per gene per cell generation- bodies contain ~1013 cells.
- only if a somatic clone occurs in relevant tissue or causes a substantially sized clone will a disease manifest
- if mutation confers growth advantage (cancer)
- if mutation occurs in early embryo
Chimeras
- a fusion of two genetically distinct zygotes