If two alleles are equal to each other the "individual is homozygous for that trait, if they are different he is heterozygous. At this point it is legitimate to ask what color is the fur of a mouse carrying two different alleles for the" hair color "trait. The answer is related to the concept of dominant character.
A dominant trait is defined as a trait that is predominantly expressed with respect to another called recessive trait. The dominant character is therefore "stronger" and able to obscure the manifestation of the weaker character. For example, if the "dark hair" character is dominant over the "light hair" character, the mouse carrying both alleles will inevitably have dark fur.
Although it is apparently hidden by the presence of the dominant trait, the recessive trait is still contained in the genetic code of the individual and as such can be transmitted to future generations.
When it comes to blood groups, character B and character A are dominant over 0.
It therefore means that if the pair AA or copy A0 is present, the result of the analysis of the blood group will still be A and the same is true if the pair of alleles is equal to B0 and BB.
A dominant trait is that which manifests itself and prevents the appearance of the other trait. Blood group A is a dominant trait because it prevents blood type 0 from appearing.
Blood group B is also a dominant trait:
Genotype (DNA) Blood group A0 or AA TO AB AB B0 or BB B. 00 0
Only if the blood group gene has both alleles 0 (allelic pair 00) will your blood test result in "group 0".
The same is true when considering the Rh factor, since Rh + is dominant with respect to Rh-. A person with a positive Rh factor may carry the allelic pair (Rh + Rh + or Rh + Rh-). On the other hand, subjects with Rh- are necessarily carriers of both Rh- alleles.
This last point allows us to open a small parenthesis, essential for the understanding of the blood group test. The germ cells (egg and sperm) are in fact equipped with only one allele for the blood group character. A father with A0 allelic couple. will produce 50% of spermatozoa with allele A and 50% of spermatozoa with allele 0. If, on the other hand, the father has group 00, AA or BB, all his gametes will respectively carry the allele 0, A or B. be made for the mother.
At the moment of fertilization, the union of the two cells will give rise to an individual with a genetic profile inherited half from the father and the remaining 50% from the mother.
Let's see an example:
two parents of group A can have both a child of group A and one of group 0;
FATHER TO 0 MOTHER TO AA (blood group A) A0 (blood group A) 0 A0 (blood group A) 00 (blood group O) Possible genotype of the son
if one or both parents have the AA allelic pair, all offspring will have blood group A
Once you understand the mechanism you can have fun calculating individual cases. Let's see, for example, why in the second table some small boxes appear obscured
A mother with blood group 0 must necessarily have the allelic pair 00, consequently all the egg cells produced will have the allele 0.
Other articles on "Blood group alleles"
- Blood group
- Blood group calculation quiz
