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What happens when genes don't follow Mendel's rule of dominant and recessive?
What happens when genes don't follow Mendel's rule of dominant and recessive?
Incomplete Dominance
Incomplete Dominance
In incomplete dominance, there is no recessive allele. Both alleles are expressed and are blended together. Since they are both dominant, both alleles are represented by different upper case letters. (Example: RR= red, WW= white, RW= pink)
In flowers, petal color demonstrates incomplete dominance. Red results when a flower has homozygous dominant alleles for the trait. White results when a flower has homozygous dominant alleles for the trait. A flower that is heterozygous for this trait will be pink.
Codominance
Codominance
Both alleles of a gene are expressed in heterozygous offspring. To distinguish between Incomplete and Codominance the allele is written as an uppercase C (codominance) with the actual allele written as superscript. See genotype examples.
Common examples include spotted flowers, speckled chickens, and roan (spotted) cattle.
Blood type... another kind of codominance.
Blood type... another kind of codominance.
Blood type is considered codominance but since there are more than two options for alleles it is also known as "multiple alleles." Blood type can be written multiple ways. You should use an uppercase I and superscript alleles when working with blood types as this is the standard way to indicate these genotypes. See below for the proper protocol.
Blood Donations... Who can give and who can receive?
Blood Donations... Who can give and who can receive?
The basic rule of thumb is that you can't introduce any antigen that isn't already present in the blood.
For example:
Natalie has A+ blood and she tries to give blood to Matt (who is B-). Two things will happen here...
1. Matt's antibodies will not recognize the A antigen and will attack the new blood cells.
2. Since Natalie has Rh factor (+) and Matt does not (-), Matt's antibodies are going to reject that as well.
Blood can be donated to any blood type that does NOT INTRODUCE ANYTHING NEW to the blood.
Knowledge Check...
A. What blood type is the universal donor and can donate to anyone?
B. What blood type is the universal receiver and can receive blood from anyone?
C. Who can donate to blood type A+?
Check your answers...
Check your answers...
A. O-
B. AB+
C. O+, O-, A+, A-
Try this out by playing the blood typing game below! (You have to allow flash)
Try this out by playing the blood typing game below! (You have to allow flash)
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