Which traits are codominant or incompletely dominant

For codominant traits, we will focus on blood types A and B. If you want to learn about how type O fits into the mix, click here. Imagine we have one parent with type A blood and the other with type B blood. To keep things simple, we will say that the parent with type A blood is AA and the other parent with type B blood is BB.

The kids inherit A from one parent and B from the other and are AB. The tricky thing here is that the kids with AB blood type have type A and type B blood rather than just a blend of part A and part B. So that the A allele makes A and the B allele makes B.

Think about A and B like marbles. Red and white marbles do not make pink marbles. You still have a mix of the two different kinds of marbles.

Same thing with A and B blood types! As you can see, depending on what the gene does, a trait can be dominant and recessive, incomplete dominant, or codominant. These situations are determined by how the different alleles for that trait interact. By Amanda Jacobson, Stanford University. Depending on how the genes involved work, a trait can be dominant, codominant or incompletely dominant.

Red blood cells and flower from Wikimedia Commons, redhead from Flickr. Incompletely dominant traits are a lot like mixed paints.

Codominant traits don't mix any better than marbles. The Tech Interactive S. Market St. San Jose, CA The Tech is a registered c 3. Federal ID Incomplete Dominance in Plants The science of genetics began with plants. Incomplete dominance was first recorded in plants.

The German scientist Josef Kolreuter bred red and white carnations, expecting to get offspring with the dominant red coloration. Instead, many came up pink! Kolreuter found that neither allele was fully dominant in his flowers and identified the concept of incomplete dominance.

Four-o-clocks are flowering plants that get their funny name from their inclination to bloom in the late afternoon. Wild four-o-clocks tend to have red flowers, while "pure" four-o-clocks with no coloration genes are white.

Mixing the two results in pink flowers, just like Dr. Kolreuter's carnations. Those pink flowers are a result of incomplete dominance. That ratio - a quarter like one parent, a quarter like the other, and the remaining half different from either - is common in cases of incomplete dominance. Pink snapdragons are a result of incomplete dominance. Cross-pollination between red snapdragons and white snapdragons result in pink when neither the white or the red alleles are dominant.

The fruit color of eggplants is another example of incomplete dominance. Combining deep purple eggplants with white eggplants results in eggplants of a light violet color. Incomplete dominance is a key element of improving crops such as corn.

Corn with multiple incompletely dominant traits is generally healthier and provides greater yields than "purer" strains with fewer such traits.

Practice: Non-Mendelian inheritance. Next lesson. Current timeTotal duration Google Classroom Facebook Twitter. Video transcript - [Voiceover] So today we're gonna talk about Co-Dominance and Incomplete Dominance, but first let's review the example of a blood type and how someone with the same two alleles coding for the same trait would be called homozygous and someone with different alleles would be called heterozygous.

Also remember, the concept of dominant and recessive alleles and how the A allele is dominant over the O allele in this example. This means that the same phenotype, blood type A, can result from these two different genotypes.

Now, the example that I just gave you was an example of Complete Dominance. So if a person had a genotype AO, since our phenotype is just blood type A, it means that the A allele is completely dominant over the O allele and only the A allele from the genotype is expressed in the phenotype. But there are actually three different patterns of dominance that I want you to be familiar with and to explain this I'm going to use a different example.

One parent flower was red and the other was white. This is an example of which of the following forms of inheritance? In the example above, the flower has both red and white petals due to co-dominant inheritance pattern of the red and white petal alleles. Polygenic inheritance occurs when two or more genes control one characteristic, such as skin color, eye color, and adult height. A sugar flower has white petals, and is homozygous for this trait. Another sugar flower is homozygous for red petals.

The white and red sugar flowers are crossed, and produce offspring with pink petals. Which of the following terms describes this type of inheritance? Incomplete dominance is described by a phenotype that is not completely dominant over another. Therefore, it will be a "blending" of colors in the case of this question, therefore the petals are pink.

Codominance is when both dominant traits are expressed, therefore if white was considered dominant and red was also a dominant trait, the petals would have spots of white and red, with no pink.

Polygenic inheritance is described by one characteristic influenced by multiple genes, which is not the case in this problem. Finally, epistasis involves the suppression of genes, however in this problem color is not suppressed. If you've found an issue with this question, please let us know. With the help of the community we can continue to improve our educational resources.

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Thus, if you are not sure content located on or linked-to by the Website infringes your copyright, you should consider first contacting an attorney. Hanley Rd, Suite St. Louis, MO We are open Saturday and Sunday! Subject optional. Email address: Your name:. Possible Answers: Dominance. Correct answer: Incomplete dominance. Explanation : A phenotypic "blending" of two traits is referred to as incomplete dominance, indicating that neither trait is truly dominant over the other.

Report an Error. Two pure breeding plants are crossed. One plant has red flowers and the other has white flowers. Possible Answers: Half of the offspring would have red flowers, and half would have pink.

Half of the offspring would have red flowers, and half would have white. All offspring would have both red and white flowers. Correct answer: All offspring would have pink flowers. Explanation : The genotypes of the offspring can be determined by crossing the red flowers, RR , with the white flowers, rr.

RR x rr Offspring: all offspring are Rr.