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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?
This video does a very good job at explaining these concepts.
This video does a very good job at explaining these concepts.
Please Watch.
Please Watch.
Incomplete Dominance: both alleles are dominant and are blended evenly
Incomplete Dominance: both alleles are dominant and are blended evenly
In incomplete dominance, there is no recessive allele. Both alleles are equal 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: in which both alleles fight for dominance, resulting in both being expressed
Codominance: in which both alleles fight for dominance, resulting in both being expressed
With Codominance, both alleles of a gene are dominant and both are expressed in heterozygous offspring.
With Codominance, both alleles of a gene are dominant and both are expressed in heterozygous offspring.
Common examples include spotted flowers, speckled chickens, and roan (spotted) cattle.
Common examples include spotted flowers, speckled chickens, and roan (spotted) cattle.
To distinguish between Incomplete and Codominance the allele is written as an uppercase C (codominance) with the actual allele written as superscript. See genotype in the chicken examples.
To distinguish between Incomplete and Codominance the allele is written as an uppercase C (codominance) with the actual allele written as superscript. See genotype in the chicken examples.
Blood type... another kind of codominance.
Blood type... another kind of codominance.
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 anything 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.
Blood type is special because there are multiple alleles involved.
Blood type is special because there are multiple alleles involved.
Blood type A and B are both codominant
Blood type O is recessive
Possible Genotypes:
Blood type A: AA or Ao
Blood type B: BB or Bo
Blood type AB: AB
Blood type O: oo
Some people also have Rh factor. If you have it, you are + and if you don't, you are -
Knowledge Check...
A. What blood type is the universal donor and can donate to anyone (hint: it can't give anything new to anyone)?
B. What blood type is the universal receiver and can receive blood from anyone (hint: it already has everything)?
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!
Try this out by playing the blood typing game below!
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