Complete, Incomplete Dominance and Codominance - difference explained
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- เผยแพร่เมื่อ 24 ก.พ. 2014
- Complete dominance
Complete dominance occurs when the phenotype of the heterozygote is completely indistinguishable from that of the dominant homozygote.
Incomplete and semi-dominance
Incomplete dominance (also called partial dominance) occurs when the phenotype of the heterozygous genotype is distinct from and often intermediate to the phenotypes of the homozygous genotypes. For example, the snapdragon flower color is either homozygous for red or white. When the red homozygous flower is paired with the white homozygous flower, the result yields a pink snapdragon flower. The pink snapdragon is the result of incomplete dominance. A similar type of incomplete dominance is found in the four o'clock plant wherein pink color is produced when true-bred parents of white and red flowers are crossed. In quantitative genetics, where phenotypes are measured and treated numerically, if a heterozygote's phenotype is exactly between (numerically) that of the two homozygotes, the phenotype is said to exhibit no dominance at all, i.e. dominance exists only when the heterozygote's phenotype measure lies closer to one homozygote than the other.
When plants of the F1 generation are self-pollinated, the phenotypic and genotypic ratio of the F2 generation will be 1:2:1 (Red:Pink:White) for both generations.
Co-dominance occurs when the contributions of both alleles are visible in the phenotype. To indicate that two alleles are co-dominant (and that neither is dominant over the other), they are both written in upper-case, with a superscript to indicate the different alleles.
For example, in the ABO blood group system, chemical modifications to a glycoprotein (the H antigen) on the surfaces of blood cells are controlled by three alleles, two which are co-dominant to each other (IA, IB) and dominant over the recessive i at the ABO locus. The IA and IB alleles produce different modifications. The enzyme coded for by IA adds an N-acetylgalactosamine to the membrane-bound H antigen. The IB enzyme adds a galactose. The i allele produces no modification. Thus IA and IB alleles are each dominant to i (IAIA and IAi individuals both have type A blood, and IBIB and IBi individuals both have type B blood. But IAIB individuals have both modifications on their blood cells and thus have type AB blood, so the IA and IB alleles are said to be co-dominant.)
Another example occurs at the locus for the Beta-globin component of hemoglobin, where the three molecular phenotypes of HbA/HbA, HbA/HbS, and HbS/HbS are all distinguishable by protein electrophoresis. (The medical condition produced by the heterozygous genotype is called sickle-cell trait and is a milder condition distinguishable from sickle-cell anemia, thus the alleles show incomplete dominance with respect to anemia, see above). For most gene loci at the molecular level, both alleles are expressed co-dominantly, because both are transcribed into RNA.
Co-dominance, where allelic products co-exist in the phenotype, is different from incomplete or semi-dominance, where the quantitative interaction of allele products produces an intermediate phenotype. For example in Co-dominance, a red homozygous flower and a white homozygous flower will produce offspring that have red and white spots. When plants of the F1 generation are self-pollinated, the phenotypic and genotypic ratio of the F2 generation will be 1:2:1 (Red:Spotted:White). These ratios are the same as those for incomplete dominance. Again, note that this classical terminology is inappropriate - in reality such cases should not be said to exhibit dominance at all.
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I’m here for this video in 2021 because of my genetics exam tomorrow and this video has just made me understand this concept so much. Thank you 😊
Glad it helped!
Thank you so much! I finally get it. Thanks for sharing.
clearly stated....thank you very much
Thank you so much. I have my genetic final exam tomorrow and the simplicity of this saved my life :)
+Racheal ZUU Good luck on your finals.
Awesome video. Thanks for the help!!!
thank you for taking time to make this video! really helpful
You are welcome! Thanks for watching.
Great Video!You rule!
this was SO helpful and straight to the point. thank you so much!
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About to take my midterm thanks a lot for this video, you explained it better than the prof.
Glad it was helpful!
Thanks 🙏🏽 this video help me so much I couldn’t find the difference between incomplete dominance and complete dominance , love from 🇮🇶
Glad it helped!
Thank you very much!!
You're welcome!
thanks that helped me a lot
thank you
Thank you so much for this! Whoosh I can finally answer my modules, Thanks!
Happy to help!
Спасибо, помог очень сильно, готовлюсь к экзамену. Thank you )
Всегда, пожалуйста.
Ты в России учишься?
Ты в России учишься?
Great video!!! Thank you :)
You're welcome! Thanks for watching.
Спасибо, мне ваш видео очень помог 👍🏽
Пожалуйста.
Outstanding fantastic explaination . this video cleared my all doubt related to to this video . Thank you so much SIR 👍👍👍👍.
You are most welcome
thanks for making it easy to learn..
+Paulmadhan Singh You're welcome! Thanks for watching.
i like ur accent. thanks for the video
You are welcome! Thanks for watching.
Well delivered🌋🌋🌋🌋
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I couldn't understand how two heterozygous traits give you two different dominance in the progeny
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Hi !
Could you please show me how to solve a question like this :
You are self-crossing DdEEffGg
and asked ---
what fraction of the resulting individuals will be homozygous recessive
at 2 or more loci?
Hi, I have many videos like that where I show step by step how to solve such problems - please search my playlists.
Here is some of my videos that can help you:
How to calculate homozygous condition as a result of the cross
How to solve problems and find genotype/phenotype as result of the cross?
What is the probability to get specific genotype as result of the cross of the parent's genotypes
Here is one more video how to solve your problem: Law of Probability and Genetics
I have a problem in color of the horse Pale cream is breeded with chesnut color and produce palominos should i aplly incomplete dominance here?
+masshuu gabureiru Send me here your problem and I will take a look and show a solution.
+Nikolay's Genetics Lessons
some investigators found that mating between horses with pale cream color to horses with chestnut coat color produced exclusively "palomino" individuals with intermediate coat color. a. number of matings between palominos themselves produced 19 pale cream,21 chesnut and 44 palominos
(a) using the first letter of alphabet defune gene symbols and suggest genotypes for three coat colors .
(b)if palomino horses breeder wanted to eliminate the pale cream individuals both as parents and as offspring , but nevertheless wanted to obtain as many palominos as possible, what breeding method would you suggest that he follow?
+masshuu gabureiru Here is a solution of your problem: th-cam.com/video/w4MMeTuSFoc/w-d-xo.html
your accent is very good. Are you from Russia? I liked that.
Yes, I'm from Russia.
What is the difference between IAi and IAIA in blood type A?
1,2 - genotypes 3 - phenotype
A homozygous IAIA or heterozygous IAi individual will have type A blood.
The RBCs of this individual will contain the surface antigen known as A.
Assuming a hereditary disease, D is inherited as an incomplete dominant trait. Will a child with Dd genotype copy of this trait be sick? It is known that those with DD genotype do die.
Please answer this. It's a similar question I'm preparing for exams next week Monday
Yes. But do not mistake incomplete dominance and incomplete penetrance - these are two different things.
@@GeneticsLessons okay
Can I count DD as one of those affected during my calculations?
Since DD eventually dies
Depends on the method - if DD unborn probably not. (stillbirth or selfabortion)
If DD dies after the birth - then yes.
@@GeneticsLessons okay
Thanks so much. I understand. We have consultation tomorrow prior to the exam which is on Monday 6th June.
I'll ask in the hall to see their responses 😃
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