In: Biology
According to Mendel’s law, phenotypical characteristics are determined by pairs of factors (alleles) that separate independently in gametes. What are the main types of inheritance that are exceptions to Mendel’s rules?
The exceptions to mendilian inheritance :
Polygenic traits: Some characters determined by
morethan one pair of genes. Eg. Human height, skin color etc.
Intermediate Expression or incomplete
dominance: In heterozygous condition due to blending
intermediate phenotype expression occurs due to lack of complete
dominance.
Eg. Flower color in 4'O clock plant. Pink is the example for
incomplete dominance, where as Red and white are due to homozygous
alleles.
Codominance: In heterozygous condition, both
alleles expresses her characters.
Eg. Blood groups such as ABO and MN systems.
Incomplete penetrance: Some of the genes does
not show their effect untill cetrain factor are present.
Eg. Multiple sclerosis in humans.
Sex-limited genes : These genes inherited by
both sexes but these will be expressed in only one sex.
Eg. Facial hair.
sex-controlled genes : These genes inherited by both sexes but expression in both sexes differently. Eg. Gout disease. This gene expressed more in man than woman.
Pleiotropy: A single gene controls expression
of morethan one trait.
Eg. Albinism.