The law of segregation says that in hetrozygotes, dominant and recessive alleles remain together without mixing into one another. In incomplete dominance, two alleles blend with each other, and the hetrozygote is a new individual with blend of both. So can it mean that incomplete dominance does not follow the law of segregation and also the law of dominance? What about law of segregation? Does it follows it?

  • $\begingroup$ Hello @Rabik Why do you mean by "mixing into one another"? Do you mean phenotypes are not mixing? Alleles are versions of a gene, so they don't really "blend" or anything, what could happen is dominance of one over the other making the phenotype look like the expression of the dominant allele. $\endgroup$
    – Untitpoi
    Mar 1, 2018 at 7:35
  • $\begingroup$ I mean each allele, either dominant or recessive. Maintain its individuality one is dominant over other but they donot blend ;according to law of dominance ,and incomplete dominance disobeys this,so I just wanted to know that does incomplete dominance obeys law of segregation? $\endgroup$
    – Rabik John
    Mar 1, 2018 at 11:27

1 Answer 1


I think you are mixing different notions, you need to be clear on what you are talking and then your answer will appear as evident to you. I invite you to check this site to get the definitions. Firstly

What is law of segregation also called first law of Mendel?

It is the hypothesis that during the formation of reproductive cells (gametes), pairs of hereditary factors (alleles of genes) for a specific trait separate so that offspring receive one allele from each parent.

Note that there is nothing here about expression (which is what is visible), it's all about genes and alleles.

What is law of dominance also called third law of Mendel?

It states that one of the allele for a pair of inherited allele will be dominant and the other recessive.

This one is about expression, you know you can have two different alleles but this law says one will always be dominant over the other (which means the allele will be expressed whether the other one will be silenced or not visible).

And what about incomplete dominance?

Well Mendel during his studies encounter more complicated case than simple dominance, sometimes the two alleles will express equally (co-dominance) giving a third observable phenotype (like blood-type AB for example). In reality, most of time the observable phenotype is nearer of one phenotype given by the domniant allele.

To conclude: incomplete dominance doesn't break the first law of mendel (segregation) as alleles will be equally transmitted to offspring but it breaks the law of dominance because the phenotype is not exactly one given by a unique allele but rather a mix between both.
Remember: Segregation law is not about expression or phenotype

  • $\begingroup$ What a perfectly phrased answer +1 $\endgroup$
    – Remi.b
    Mar 1, 2018 at 16:13
  • $\begingroup$ Thanks untitpoi!I will make my basics more strong. There is one more thing that bothers me a lot that;one allele is a pair of genes on homologous chromosomes. I wanted to know that in a pair of homologous chromosomes there are two alleles on" each" chromosome ? Or there is only one allele on "both" ?Or it's like that out of a pair of genes in allele one gene is on one chromosome and other gene is on another homologous chromosome? $\endgroup$
    – Rabik John
    Mar 2, 2018 at 4:45
  • $\begingroup$ For one given gene, there could be multiple version of that gene in a population like allèle A B and O for blood type. But one individual only has two alleles one coming from mom and one from dad. What could have make you think there is four allèle per individual is the bad double chromosome visualisation(In X form you know). But that happens only during meiosis and is NOT the normal state of DNA $\endgroup$
    – Untitpoi
    Mar 2, 2018 at 7:40

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