What are the exceptions to the $-$
Law of dominance
Law of independent assortment
- Law of segregation
My knowledge:
Exception of law of dominance:
Incomplete dominance
In incomplete dominance when a red snapdragon flowered plant is crossed with a white flowered plant an intermediate phenotype appears in the F1 hybrid instead of a parental phenotype.
Codominance
Unlike dominance in codominance when a A ($I^AI^A$) blood group individual mates with B ($I^BI^B$) blood group individual the offsprings have blood group AB ($I^AI^B$) instead of A or B.
Exception of law of segregation:
Nondysjunction
During meiosis homologous chromosomes/sister chromatids and hence genes may move to a common gamete violating law of segregation.
Exception of law of independent assortment:
Linkage
When genes are present on the same chromosome they tend to remain together and enter into the same gamete. This is the reason behind deviation of dihybrid test cross ratio from 1:1:1:1 and occurrence of parental combination in high frequencies.
Am I correct? Are there any more exceptions to these laws?
Answer
You are right but the list is certainly not exhaustive. Here are a few more concepts you may want to consider.
Exception of law of dominance:
epistasis
Allelic effect at a given locus depend on the variants at other loci
environment dependence and specific case of frequency dependence
The concept of dominance can be used for any quantitative trait. Typically, when the quantitative trait of interest is fitness, then the trait often depend on the environment. A typical and interesting case is when the fitness depends on the frequency of alleles in the population. Depending of the frequency of the allele at a given locus, the relationship might be a relationship of dominance, additivity or dominance for the other allele.
Exception of law of segregation:
meiotic drive
from wiki: "Meiotic drive is a type of intragenomic conflict, whereby one or more loci within a genome will affect a manipulation of the meiotic process in such a way as to favor the transmission of one or more alleles over another, regardless of its phenotypic expression. More simply, meiotic drive is when one copy of a gene is passed on to offspring more than the expected 50% of the time."
Exception of law of Independent assortment:
epistasis for fitness
Imagine a case where a given combination of allele is lethal at very young age, then you would never see these two alleles together in an individual. It is per se, not a case of exception to independent assortment but it gives the feeling of such exception. A case more extreme when a given combination of alleles prevents fecundation could however be considered as an exception to independent assortment.
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