I'm confused by these terms in genetics, is there anyone who can tell me the difference? Thank you!
Co-dominant inheritance is that in which no allele exert dominant effect on other one (for a pair of alleles). Incomplete dominance is those in which a allele is mostly dominant, but we can observe a partial manifestation from the other one. Over-dominant, is the first time I have read about this, but may be an allele that exerts dominant effect on a group of alleles. In a gene different alleles may show different inheritance ways.
Over-dominance describes that an allele is advantageous when observed at a heterozygous loci (so heterozygote advantage). Balancing selection can operate by over-dominance maintaining many recessive or co-dominant alleles, which have increased fitness benefits when expressed with other alleles. This is hypothesized to be a mechanism responsible for high MHC gene diversity.
Hi Dr. Fernando,
Thank you for your explanation. The definition is somewhat abstract, but I have got what I want to know. In genetic linkage analysis, genetic markers are very important. But I have no idea why microsatellites are co-dominant markers?
interesting question for I had never heard about incomplete dominant and over-dominant.
It seems these concepts are weired.
Dominant mean the phenotype is the same that the homozygote with the dominant allele and co-dominant mean phenotype is intermediate. but exact midle is hard to evaluate.
An exemple of misclassified allele in the dominant/codominant is the curly wings phenotype of Drozophila. Often we here it is dominant… well no, it is observed only in heterozygote for homozygote with that allele is lethal… then it is codominant, with an intermediate state between a normal phenotype and a lethal state.
Effect of phenotype depends on expression of gene and nature of gene action. Generally it is hybrid of parents one copy from each i.e. heterozygous. If the action of allele is intermediate between two that is partial dominance. If both alleles are expressed that is co-dominance means neither is recessive.
Individuals carry no copy or one copy or two copies of the marker allele. Additional copy of allele either additivity, or dominance or recessive or over dominance. This can be done by statistical analyses
1. If the relationship between alleles is 'additive' i.e. d=0 phenotype of hybrid is 'intermediate' between parents.
2. If the relationship between alleles is either 'dominant' i.e. d=a or ‘recessive’d=-a then the phenotype of hybrid is identical to one of the parents.
3. If the relationship between alleles is 'overdominant' i.e. a=0, d>0 then the phenotype of hybrid is 'incremental effect over both the parents'.
(Ref. M. Maheswaran. Mapping Quantitative Trait Loci in Plants: Approaches and Applications)
Hi, all! Thank you for your reply anyway! I just find a good explanation on the website,
http://en.wikipedia.org/wiki/Dominance_(genetics)
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