The process underlying differences in expression of a gene, according to which parent has transmitted, is called- (AIIMS May 2014)
There are functional differences between paternal and maternal genes. So the expression of gene will be different ' depending on, whether it has transmitted by father or mother. This is called genomic imprinting (also see previous explanations).
o In genetics, anticipation is a phenomenon where by the symptoms of a genetic disorder become apparent at age earlier age as it is passed to next generation.
o In most cases, an increased severity of sympioms is also noted.
o Anticipation is se en in trinucleotide repeat disorders, e.g. huntigton's disease, myotonic dystrophy, Fragile 'X' syndrome and Friedreich ataxia.
o Mosaicism is the occurence of two or more different types of cell populations in the same individuals.
o For example same individual have cells having 45X and 47, XXX i.e. 45 X / 47 XXX mosaic.
o Some individuals inherit the mutant gene but are phenotypically normal. This is referred as nonpenetrance.