Introduction to Non-Mendelian Inheritance
Biology: IB Diploma Higher Level, topic 15.1.5
Non-Mendelian Inheritance
Further genetic studies have shown that some patterns of inheritance do not follow the patterns predicted by Mendelian genetics.
Mendel's laws
- Mendel’s laws suggest that:
- Two “units” or alleles exist for every gene
- Alleles maintain their integrity in each generation (no blending)
- In the presence of the dominant allele, the recessive allele is hidden and makes no contribution to the phenotype.
- Therefore, recessive alleles can be “carried” and not expressed by individuals.
- Such heterozygous individuals are sometimes referred to as “carriers.”
Exceptions to Mendel's laws
- Further genetic studies in other plants and animals have shown that much more complexity exists, but that the fundamental principles of Mendelian genetics still hold true.
- Exceptions to Mendel's law are observed when the phenotypic ratios predicted by Mendelian inheritance are not followed in the F2 progeny.
- So, a monohybrid cross would not show a 3:1 inheritance pattern and a dihybrid cross would not show a 9:3:3:1 inheritance pattern.
Test yourself on Introduction to Non-Mendelian Inheritance
Which of the following is NOT suggested by Mendel's laws?
Which of the following is NOT suggested by Mendel's laws?